Manchester attack: UK terror threat level raised to critical
The UK terror threat level has been raised to its highest level of "critical", meaning further attacks may be imminent, Theresa May has said.
By Dominic Casciani, BBC home affairs correspondent
This is a major and very rare move by the UK's security chiefs.
For the past few years, ministers, police chiefs and others have been at pains to try to warn the public that the threat faced by the UK was severe.
But they have steered clear of warning, even when a major plot was being tracked, that an attack could be close. This time, they feel they have no choice other than to say it may be imminent.
In short, nobody at this stage can say for sure whether Abedi acted alone or with the help of others. They can't rule out if there are other people out there.
What does it mean for us, the public?
Some of us will see the Army in key locations that need guarding so that armed police can be freed to focus on policing rather than guarding.
We should expect additional time-consuming security checks at ports and so on.
The aim for security chiefs is to ratchet up the security while keeping the country moving.
The UK terror threat level has been raised to its highest level of "critical", meaning further attacks may be imminent, Theresa May has said.
AnalysisMove came after investigators were unable to rule out whether Manchester bombing suspect Salman Abedi acted alone, the prime minister said.
The first time the threat level was raised to critical was in 2006 during a major operation to stop a plot to blow up transatlantic airliners with liquid bombs.
Military personnel will now be deployed to protect key sites.
By Dominic Casciani, BBC home affairs correspondent
This is a major and very rare move by the UK's security chiefs.
For the past few years, ministers, police chiefs and others have been at pains to try to warn the public that the threat faced by the UK was severe.
But they have steered clear of warning, even when a major plot was being tracked, that an attack could be close. This time, they feel they have no choice other than to say it may be imminent.
In short, nobody at this stage can say for sure whether Abedi acted alone or with the help of others. They can't rule out if there are other people out there.
What does it mean for us, the public?
Some of us will see the Army in key locations that need guarding so that armed police can be freed to focus on policing rather than guarding.
We should expect additional time-consuming security checks at ports and so on.
The aim for security chiefs is to ratchet up the security while keeping the country moving.