The number of armed police officers in Scotland is to increase by a third to prepare the country for terror attacks and gun crime.

The force, which currently has 275 officers attached to armed response vehicles (ARVs), has announced plans to add a further 90 to that capability.

The change, expected to be in place by the spring or summer of next year, will lift the number of routinely-armed officers to 365, a jump of about 33 per cent.

Overall, the force is to boost the number of officers within armed policing by 124 - a figure which also includes trainers and specialist firearms officers.

Police chiefs said the increase - announced days after terror attacks in Orlando and France - is in response to the latest assessments of the threat from terrorism and the use of firearms by home-based criminal gangs.

They stressed it was not being taken in response to any specific threat to Scotland.

They also said the force overall remains an "unarmed service", with the changes meaning that less than three per cent of its 17,234 officers will be deployed in a firearms capacity north of the border.

Assistant Chief Constable Bernard Higgins said: "The threat level to the UK remains severe.

"There is no specific known threat to Scotland and this increase is not a response to any direct intelligence; but we must play our part in ensuring the safety and security of the whole of the UK.

"It would be dangerous and complacent to think that Scotland is any less at risk than the rest of the UK and this move helps enhance our response."

It is understood the planned changes will take the total number of firearms-trained officers from around 350 to 474.

Mr Higgins said: "We are an unarmed service. Even with this increase of 124 officers that will still be a very modest number of full-time officers deployed on firearms duties."

Scottish Police Authority (SPA) board member Iain Whyte said the body was satisfied that an increase in the number of armed officers in Scotland of this scale is "proportionate, based on an assessment of the current threat level, and necessary to ensure Police Scotland is as prepared as possible to respond and counter the range of threats that may occur".

Holyrood Justice Secretary Michael Matheson said Police Scotland's decision has the full backing of Scottish ministers and confirmed armed officers will remain restricted from routine deployment following an outcry over their attendance at minor incidents and public places such as supermarkets.

Mr Matheson said while there is no specific intelligence "the threat we face from terrorism is real".

Brian Docherty, chairman of the Scottish Police Federation said "it will go some way to addressing the concerns we have expressed for some time over the preparedness of the service in Scotland to deal with a terrorist attack".

"That being said we remain absolutely conceded that the scale of cuts to the police budget in its own right fundamentally undermines not only the fight against terrorism but also

against crime in general.

"Additionally there is an inevitability that with less money the wider provision of general police service will diminish."

John Finnie, justice spokesman for the Scottish Greens and MSP for the Highlands & Islands, said: "The Justice Secretary must accept that there will be serious public concern about today's announcement. Although there is information informing the threat level, we must question the quality of the intelligence received and whether it has been obtained legitimately, especially in light of recent revelations about the Scottish Recording Centre."