Police have appealed for footage afer eight people died when a police helicopter crashed into the roof of a crowded pub in the centre of Glasgow.

The three occupants of the helicopter - two police officers and a civilian pilot - were among the dead, Police Scotland said.

Special prayers will be said and candles lit for the victims at a service at Glasgow Cathedral tomorrow.

Justice Secretary Kenny MacAskill will attend the service at 11am.

Officers from Police Scotland's Major Investigations Team are asking the public to send any photographs, audio or video footage they have of the incident or the surrounding areas to a dedicated email address which has been set up to receive media.

Anyone who has footage is asked to send it to glasgowhelicopterincident@scotland.pnn.police.uk.

Chief Constable Sir Stephen House said: "Our thoughts and condolences are very much with the families of those who have died and those who have been injured in this tragic incident.

"We are working alongside our emergency services colleagues in the ongoing rescue operation. I would like to take this opportunity to praise the people of Glasgow who helped in the very early stages following the incident and commend their courage.

"We are dealing with a very sensitive and complex operation and we expect that emergency services will be at the scene for some time. We would thank the public for their co-operation as our officers and other emergency service colleagues continue this difficult task."

Fourteen people remain in Glasgow hospitals, he said.

The Queen said her "thoughts and prayers" were with the victims of the crash.

In a personal statement, she wrote: "I was saddened to learn of the dreadful helicopter crash in Glasgow last night.

"My thoughts and prayers are with those who have been bereaved or injured.

"I send my thanks to the emergency services and to everyone who helped with the rescue.

"Elizabeth R."

Witnesses said the helicopter came down "like a stone" from the sky and hit the roof of The Clutha at 10.25pm yesterday.

Members of the public formed a human chain to help remove those inside the popular music venue in Stockwell Street.

Sir Stephen gave an update at the scene of the crash, close to the River Clyde.

Well over 100 people were inside the pub listening to a band when the helicopter came through the roof, he said.

"Three of these eight fatalities were found within the helicopter and were our colleagues in the helicopter crew," said Sir Stephen.

"The remaining five people were found within the building.

"Fourteen people remain seriously injured in Glasgow hospitals, who are being cared for by health colleagues there.

"A major investigation is under way by the police under the direction of the Crown Office and Procurator Fiscal Service and by the Air Accidents Investigation Branch.

"Together with colleagues from Scottish Fire and Rescue Service and the Scottish Ambulance Service, Police Scotland officers are working to rescue and recover within the premises behind us."

Rescuers are working in a "complicated and dangerous" environment.

"This is a complex and ongoing rescue operation. It will not be a quick operation. It's a very complicated and indeed dangerous scene. I pay tribute to those people from the emergency services who are working in and around the scene," he said.

"I'd also like again to commend the courage of the people in Glasgow who, heedless for their own safety, took action last night at the time of the incident, and the many acts of kindness we've seen since.

"Particularly I've been asked to mention the fact that many of the rescue workers are grateful to the Holiday Inn Express. The nearby hotel has thrown open its doors to provide food and shelter for the rescue staff as they go about their job.

"We are dealing with a very sensitive investigation and operation here. It will go on for many days yet."

The injured were taken to Victoria Infirmary, Glasgow Royal Infirmary and Western Infirmary.

The aircraft involved was a Eurocopter EC135 T2.

A large section of the city centre is cordoned off with all roads leading to the junction of Clyde Street, Stockwell Street, Bridgegate and Victoria Bridge closed.

Police set up a telephone number for members of the public concerned about relatives who may have been involved in the crash. It is 0800 092 0410.

First Minister Alex Salmond described today, St Andrew's Day, as a "black day for Glasgow and for Scotland" and ordered flags to fly at half-mast outside government buildings.

He visited the multi-agency command centre in Glasgow with Sir Stephen, other emergency services and Scotland's Justice Secretary, Kenny MacAskill.

"All of us have seen over the last few hours, the speed and effectiveness of the mobilisation of the emergency services in dealing with this tragedy," he said.

"We've also heard of the instinctive courage of ordinary Glaswegians going to assist their fellow citizens in extremity.

"This is a black day for Glasgow and Scotland but it's also St Andrew's Day, and it's a day we can take pride and courage in how we respond to adversity and tragedy."

Flags were also lowered to half-mast outside the Scottish Parliament building in Edinburgh.

Prime Minister David Cameron said: "I want to thank the emergency services who worked tirelessly throughout the night and I also want to pay tribute to the bravery of the ordinary Glaswegians who rushed to help."

Among those helping with the rescue last night was Labour frontbencher Jim Murphy who saw a "pile of people clambering out" of the bar as he was driving past.

"I jumped out and tried to help," said the East Renfrewshire MP.

"There were people with injuries. Bad gashes to the head. Some were unconscious. I don't know how many.

"The helicopter was inside the pub. It's a mess. I could only get a yard or two inside. I helped carry people out.

"My human instinct kicked in. I didn't like what I was seeing but I did what everyone else was doing and got stuck in. I feel like I'm in shock now. It's a horrible scene."

People formed a human chain to help pass unconscious people out of the pub so that "inch by inch, we could get the people out", Mr Murphy said.

Grace MacLean, inside the pub at the time of the crash, said it was busy with people listening to a ska band.

"We were all just having a nice time and then there was like a whoosh noise. There was no bang, there was no explosion. And then there was some smoke, what seemed like smoke," she told BBC News.

"The band were laughing and we were all joking that the band had made the roof come down.

"They carried on playing and then it started to come down more and someone started screaming and then the whole pub just filled with dust. You couldn't see anything. You couldn't breathe."

Nine-piece Glasgow ska band Esperanza were on stage when the helicopter hit the roof.

Writing on their Facebook page, the band said they were "waking up and realising that it is all definitely horribly real".

They said in a statement: "Despite the situation everyone was so helpful and caring of each other. The police, ambulances (and) firefighters all did a stellar job and continue to do so today in extremely difficult conditions.

"Our biggest concern is that everyone is found and can get the care and help they need."

Gordon Smart, editor of The Sun's Scottish edition, said he saw the helicopter come down from a multistorey car park around 250 yards away.

"It was just such a surreal moment. It looked like it was dropping from a great height at a great speed," he told Sky News.

"There was no fireball and I did not hear an explosion. It fell like a stone. The engine seemed to be spluttering."

The Lord Provost of Glasgow, Sadie Docherty, said: "It is shocking, but our Glaswegian resolve will get us though this together."

The British Airline Pilots Association said the investigation will be painstaking.

"Nevertheless, trends in helicopter safety is a matter of concern after a number of recent incidents including those in the North Sea," the association said in a statement.

"We hope that ongoing inquiries by the Civil Aviation Authority and the House of Commons Transport Select Committee into helicopter safety will also have the opportunity to look into the circumstances around last night's incident too."

As Glasgwegians came to grips with the scale of the crash, local religious leaders offered their condolences.

A special Mass was held at nearby St Andrew's Cathedral.

The Archbishop of Glasgow, Philip Tartaglia, said: "My heart goes out to all those who have been affected by this tragic accident. Prayers will be offered for everyone, especially for those who have died, for the injured and for the bereaved."

Priests from the parish were on hand last night during the rescue to help the injured and relatives.

Right Rev Lorna Hood, moderator of the General Assembly of the Church of Scotland, said: "Already stories of those caught up in a tragedy forming a human chain to help those trapped show the spirit of the people of Glasgow and their care for one and other."

Speaking outside the cordoned-off bar, Sir Stephen said it is not known how many people are still in the building.

"We do not know that. We are still in what we are determining as a rescue and recovery situation. The helicopter is in there and it is dominating the whole space within the building," he said.

"Until it is out of the way, we won't know everything that is going on underneath the helicopter. We simply can't say what the situation is at this moment definitively."

He also said: "I have to ask you to imagine the situation where the helicopter has come down and is literally sitting in the middle of the building.

"Until that is resolved we can't know everything that is in that building."

Alasdair Hay, chief fire officer, said: "This is a very challenging , very complex and very difficult rescue situation.

"The Scottish Fire and Rescue service will remain here throughout working with our colleagues to ensure that we do everything that we possibly can to recover the casualties and rescue where appropriate."

Gary Hardacre, head of risk and resilience at the Scottish Ambulance Service, said that as a mark of respect, ambulance staff who work with helicopter crews at Glasgow and Inverness bases have been rested, and contingency arrangements have been put in place.

"We will be bringing those resources back on to line later on this evening and into tomorrow morning, he said.

Helicopter operator Bond Air Services said in a statement: "Bond Air Services is deeply saddened by the tragic accident In Glasgow last night. Our hearts go out to all those who have been touched by the events of Friday 29 November. We would also like to acknowledge the efforts of the emergency services who continue to work tirelessly at the scene.

"The site has been contained and a full investigation by Police Scotland into the incident has begun, under the direction of the Crown Office and Procurator Fiscal Service.

"The Air Accident Investigation Branch is also carrying out an investigation.

"Bond is working with Police Scotland, other emergency services and the Air Accident Investigation Branch as the investigations into the causes of the accident get under way."

NHS Greater Glasgow and Clyde confirmed that 14 patients remain in the city's hospitals. Eighteen people who were taken to hospital last night have now been discharged.

Dr Jennifer Armstrong, the health board's medical director, said head injuries and fractures were among the main injuries they were dealing with.

She told broadcasters: "Our well-rehearsed emergency arrangements were immediately enacted last night. Whilst I can't go into detail about individual patients, the main injuries we have seen include chest injuries, head injuries, long bone fractures and lacerations.

"I would like to thank the many staff who came into our hospitals last night to help us respond to this emergency.

"And finally I would like to express on behalf of the staff of NHS Greater Glasgow and Clyde our condolences to the family and friends of the people who died last night."

Eurocopter said an accident investigation team is on its way to Scotland to help the AAIB and other bodies.

A statement on the firm's website said: "Eurocopter confirms that an EC135 T2 operated by the Scottish police force was involved in an accident on November 29 2013 in Glasgow's city centre, with a crew of three consisting of two police officers and one pilot.

"Our thoughts are with the victims, their families, and the teams and individuals involved in the rescue operations.

"A Eurocopter accident investigation team is on its way to Scotland to assist the AAIB and BFU (the UK and German accident investigation boards). No further details are available at this stage."

In a statement on their Facebook page, The Clutha said: "Our thanks go out to all the goodwill messages and prayers for those who tragically lost their lives in the accident last night.

"An event beyond comprehension and belief. The customers who could showed the true spirit of Glasgow along with all the emergency services. Our heartfelt sorrow to all of the families of those who perished."