Troops are guarding a dozen sensitive sites in Scotland in the wake of the Manchester terror attack, but are not expected to appear on the streets, Nicola Sturgeon has said.

The First Minister said British armed forces had been deployed at nine military and three civilian nuclear sites north of the border in the first phase of Operation Temperer.

This had freed up a “contingency” pool of armed civilian officers from those sites, but Police Scotland had so far chosen not to draw upon it, as its own resources were sufficient.

She said the second phase of Operation Temperer - troops on the streets under police control - had not been activated, but was not ruled out.

Updating MSPs, she said: “We do not currently envisage that military personnel will be deployed on the streets in Scotland or in other public locations. However as with all operational matters this will be kept under review by the Chief Constable.”

She went on: “We must not allow terrorism to triumph. I urge the people of Scotland to be vigilant but not alarmed and, as far as possible, to go about their business as usual.”

She said the public would see more armed police at transport hubs and city centres, and Police Scotland were reviewing security around every public event due in the coming weeks, including Friday'svisit by President Obama, Saturday's Scottish Cup Final at Hampden, this weekend's Edinburgh Marathon, and the Lisbon Lions memorial event in Glasgow.

“The aim here is to allow public events to continue as far as possible as normal. However the public should anticipate additional safety measures at these events, and these measures may well include full body and bag searches, and the presence of armed police.

“My message to the public is this: this is clearly a very anxious time, but there is no need to be alarmed. Many of the steps that are being taken now are precautionary.

“I repeat there is no evidence of a specific threat to Scotland. However I do ask the public to be vigilant and to report any concerns or suspicions that they may have to the police.”

Operation Temperer began after the Joint Terrorism Analysis Centre raised the UK threat level from severe to critical on Tuesday night, judging a further attack may be imminent.

Monday’s suicide bombing at the Manchester Arena, which targeted parents and children leaving an Ariana Grande pop concert, left 22 dead and 64 injured.

At the Scottish Parliament, Ms Sturgeon said that after the level was raised, she convened a meeting of the Scottish Government’s resilience committee in the early hours of Wednesday morning.

It was attended by Deputy First Minister John Swinney, Justice Secretary Michael Matheson, Lord Advocate James Wolffe QC, and members of the police, fire and ambulance services.

The chief executive of the Scottish Parliament, Sir Paul Grice, was also present.

Security measures have now been stepped up at Holyrood, with all visitors and staff forced to go through scanners and searches, and a ban on liquids being carried into the building.

Ms Sturgeon said Police Scotland had established a “multi-agency coordination centre” at Govan Police Station in Glasgow, and that she would visit it herself later on Wednesday.

She said the initial phase of Operation Temperer involved troops being sent to sites normally patrolled by armed officers of the Ministry of Defence Police and Civil Nuclear Constabulary.

With military personnel taking over their duties, these armed police were then free to support other police services across the UK.

In Scotland, armed forces had been deployed to nine military bases and three civilian nuclear sites, understood to be the nuclear plants and stores at Dounreay, Torness and Hunterston.

None of the 12 sites are accessible to the general public.

Ms Sturgeon said: “The presence of military personnel at sites of this nature, both in Scotland and across the UK, will free up the armed police who are normally on duty there and these armed police will create a contingency resource which can be deployed across the UK.

“Any decision to make use of that contingency resource in Scotland would be for the Chief Constable. However Police Scotland have no plans at this initial stage to do so.”

“They have confirmed that they have reviewed security across Scotland to ensure that the right level of policing is in place and they can provide that level of policing from within their own resources. This is, of course, something that will be kept under review by Police Scotland.”

She said Police Scotland had around 600 trained firearm officers, and had doubled the number of armed response vehicles on patrol since Monday’s attack.

The First Minister stressed that only this initial phase of Operation Temperer was in force.

The second phase, were it activated, would involve military personnel guarding specific sites under the control of the police - potentially meaning troops on the streets - but this was not currently anticipated.

She also stressed the increase in armed policing was a specific response to the Manchester attack, and did indicate a long-term shift to having more armed officers on regular patrol.

Chief Constable Gormley said: "As part of Operation Temperer, chief constables across the UK have the ability to request support from the armed forces, if required.

“This option is open to Police Scotland and the situation is being reviewed, however, the service currently has sufficient resources deployed and available at present."

Scottish Tory leader Ruth Davidson said people should be vigilant but not fearful or cowed. As we face down the current threat, I know that the sight of armed police officers and service personnel at key locations may be unsettling but there can be no doubt that the response is necessary."

LibDem leader Willie Rennie agreed, stating he believed the balance had been struck on keeping people safe without creating a "climate of fear".

He said: "I have complete confidence in the painstaking and intelligent work being carried out by the security services and the recommendations they have made."

Green MSP John Finnie, a former policeman, said: “It's always disappointing to see armed officers on patrol but we must accept that the decision has been made after a careful assessment of the current risk to the public. "The First Minister's comment that this deployment does not indicate a long-term trend is welcome.

"When the current threat level reduces we must see a reduction in the use of armed officers.”