The UK terror threat level has been raised to the highest level of "critical", meaning further attacks may be imminent, Theresa May has said.
The move came after investigators were unable to rule out Manchester bombing suspect Salman Abedi acted alone, the prime minister said.
BBC reports military personnel would now be deployed to protect key sites.
Twenty-two people were killed and 59 injured when a suicide bomber attacked concert-goers at Manchester Arena.
Military personnel may also be seen at other events, such as concerts, Mrs May said, and would work under the command of police officers.
Source:
BBC