LONDON (AP) — Britons will find armed troops at vital locations after the official threat level was raised to its highest point following a suicide bombing that killed 22.

Officials say soldiers will be deployed to places like Buckingham Palace, 10 Downing Street and Parliament. They will replace armed police as Operation Temperer takes effect Wednesday.

Officials believe this will free up police to fight the threat of further extremist action against civilian targets, amid fears that another attack may be imminent

Police are trying to determine whether suicide bomber Salman Abedi acted alone when he set off his explosives at the end of a pop concert at a Manchester arena. The government Tuesday night raised the threat to "critical", its highest level, following an emergency Cabinet session.