UK raises terror threat level from "severe" to "critical"

British Prime Minister Theresa May announced Tuesday night that the country's terror threat level has been raised from "severe" to "critical", its highest level.

Members of the armed forces will be deployed across Britain under police command, and they would be seen at "big events", according to May.

"This means that armed police officers responsible for duties such as guarding key sites will be replaced by members of the armed forces, which will allow the police to significantly increase the number of armed officers on patrol in key locations," said May. "You might also see military personnel deployed at certain events, such as concerts and sports matches, helping the police to keep the public safe."

May was speaking after she chaired the second meeting of the day of Britain's top-level security committee known as Cobra.

The upgrade is in response to top level reports discussed at the Cobra meeting by Britain's most senior security advisors.

"I do not want the public to feel unduly alarmed. We have faced a serious terrorist threat in our country for many years. And the operational response I have just outlined is a proportionate and sensible response to the threat that our security experts judge we face," said May.

A statement from the Met police about these changes will come later this evening, the prime minister added.