Scotland reacted with shock and horror after Christmas shoppers were knocked to their deaths in an accident that "could hardly be more tragic".

Glasgow City Council leader Gordon Matheson described the road crash as "a terrible tragedy", while Glasgow Archbishop Philip Tartaglia said his "heart broke" for those caught up in the incident.

Mr Matheson said: ''This is a terrible tragedy and our thoughts and prayers are with all those affected, particularly the families of those who have lost their lives."

Archbishop Tartaglia said: "I was shocked and horrified to hear the news of this incident.

"My heart breaks for all those who have been directly caught up in it as they go about their business just a few days before Christmas in the centre of Glasgow.

"The circumstances could hardly be more tragic. I would ask any person of faith to pray for those who have died and their relatives and those who have been injured."

Glasgow Lord Provost Sadie Docherty said: "This is shocking and upsetting. My thoughts and prayers are with the families of those affected by this terrible incident."

Moderator of the General Assembly, Rt Rev John Chalmers, said: "The news from the city centre of Glasgow just a few days before Christmas is simply devastating.

"For the second year in a row Glaswegians will have to dig deep into their reserves of compassion and sympathy as they support the families of those who have been killed and injured today.

"I am sure that in these circumstances the churches and faith communities of Glasgow will do all that they can to bring support and comfort to those caught up in this tragedy and that all round Scotland and beyond; Glasgow will be remembered in the prayers of the people."

Political leaders in Scotland and at Westminster also expressed their shock and paid tribute to the emergency services.

Scotland's First Minister Nicola Sturgeon said: ''My thoughts are with everyone involved in this tragic incident, and especially with the friends and families of the six people who lost their lives in what is another sad day for Glasgow and Scotland.

"As ever, Scotland's emergency services have responded in a swift and professional manner and I would encourage everyone to let them get on with their vitally important roles."

Scottish Conservative leader Ruth Davidson said: "This is a terrible tragedy, right in the heart of Scotland's biggest city.

"No-one expects that ordinary people, out to do some last-minute Christmas shopping, would fail to make it home.

"Everyone's thoughts and prayers are with those who have lost loved ones today.

"Glasgow's response has been magnificent. Passers-by immediately tried to help the injured, to direct traffic and assist the emergency services. Those emergency workers showed huge professionalism treating the wounded, securing the site and making sure people stayed safe.

"Glasgow has pulled together in recent times during such senseless tragedies, and we've seen it do so again today."

Scottish Secretary Alistair Carmichael said: ''I share Scotland's deep shock at the horrible events in Glasgow this afternoon. On the eve of the festive period, these are unimaginable scenes in one of the busiest parts of our largest city.

''My thoughts are with the bereaved, the emergency services dealing with the aftermath and everyone affected by this terrible incident.''

Labour's shadow Scottish secretary Margaret Curran MP said: "This is a tragedy that will be felt not just in Glasgow but across the whole country. Everybody in Scotland will keep the families of those who have died in their thoughts and prayers.

"Details of exactly what happened will emerge over the coming hours and days. In the meantime, it is important that our emergency services are given all the support they need."

Prime Minister David Cameron said: ''I'm being kept fully briefed on the major incident in Glasgow. My thoughts are with the families of those involved and the emergency services.''

Labour leader Ed Miliband said: ''Terrible news from Glasgow - my thoughts are with all those affected by this horrific accident.''

Deputy Prime Minister Nick Clegg said: "Horrific news in Glasgow. My heart goes out to the families of all those caught up in this awful incident."

Comedian Hardeep Singh Kohli tweeted: "Poor Glasgow. #love"

TV presenter Philip Schofield tweeted: "OMG, just catching up to on the news. Thinking of everyone caught up in today's terrible accident in Glasgow #GeorgeSquare"