Armed police patrols are to be increased across Scotland following the Tube bombing in south-west London.
Police Scotland said the move was part of "well-rehearsed plans to respond to major incidents".
It came as the UK terror threat was raised to critical, meaning an attack is expected imminently, after a device was detonated at Parsons Green station.
Police Scotland said there was no intelligence to suggest there is any specific threat to Scotland.
An 18-year-old man has been arrested on suspicion of terror offences in connection with Friday's attack. He was detained in Dover on Saturday.
The Scottish Government Resilience Room has been activated following the London attack and First Minister Nicola Sturgeon and key cabinet colleagues have been "fully briefed" in connection with the increased threat level.
Police Scotland's Assistant Chief Constable, Bernard Higgins, urged the public to remain alert and report anything suspicious.
He said: "With the threat level now at Critical, Police Scotland will be increasing our operations to protect the people of Scotland, our businesses and public places.
"This will include increasing the number of armed police on patrol across the country. The public should expect to see armed officers on foot patrol at key locations and crowded places across the country."
He added: "Please do not be alarmed by the presence of these armed officers. These measures are being taken to increase security at these sites, and to reassure residents, businesses, workers and visitors so they can go about their daily lives as normally as possible.
"Along with event organisers, we will also be reviewing all significant events taking place over the next few days and will increase the security footprint around those events where it is deemed appropriate.
"We have well-rehearsed plans to respond to major incidents and we will be continuing to work with our partners to address the current heightened threat.
"However, there is no intelligence to suggest there is any specific threat to Scotland but I would ask the public to remain alert and report anything suspicious.
"Terrorists want to create discord, distrust and fear. The police stand together with all communities in the UK and we will take action against any criminal behaviour, which seeks to undermine society, especially where crimes are motivated by hate.
"Communities defeat terrorism, which is why we must maintain the strong relationship we have between the public and the police."
So-called Islamic State has said it was behind the London Tube bombing.
Twenty-nine people have been treated in hospitals, mostly for burns, following the attack at 08:20 on the eastbound District Line train from Wimbledon.
First Minister Ms Sturgeon said ministers' thoughts remained with those who sustained injuries.
She added: "While it is natural that any increase in the threat level is of concern, the public should be reassured that all appropriate precautionary measures are being implemented.
"My advice to the public is to remain vigilant and report any concerns to the police - but otherwise to go about daily life as normal."
Holyrood officials have confirmed that extra security arrangements are in place at the Scottish Parliament.
Tours and events have been cancelled while the heightened threat level exists and no liquids - except medication - will be allowed in the building.