Nearly 1,000 soldiers will be deployed in London, the traditional Changing of the Guard at Buckingham Palace has been cancelled for an “indefinite period”, and the Palace of Westminster has been closed to the public following the terror attack in Manchester Monday.

British Home Secretary Amber Rudd confirmed today that 984 military personnel will be deployed in the UK capital following the raising of the terror threat level from “severe” to “critical” on Tuesday night.

Up to 5,000 soldiers could be deployed in total, initially be deployed in London, then across the rest of the country.

Soldiers will replace armed police at sites including Buckingham Palace, Downing Street, and the Palace of Westminster as part of Operation Temperer. The deployment has been reportedly made to allow armed police to be sent elsewhere.

The Changing of the Guard Ceremony outside the Queen’s residence, Buckingham Palace, has been cancelled reportedly in response to the need for more police resources. The cancellation has been put into effect “for an indefinite period”.

Wednesday afternoon, the Metropolitan Police confirmed a man was arrested on the Mall, near Buckingham Palace, with a knife. The man was arrested on suspicion of a possession of an offensive weapon, and was taken into custody at a central London police station. The incident is not believed to be terrorism related.

The Palace of Westminster, which houses the House of Commons and House of Lords, has also been closed to non-pass holders. All tours to the general public have been suspended.

Security has been increased in Westminster following the terror attack earlier this year which claimed the lives of five people including PC Keith Palmer who was guarding Westminster Palace gates.

Authorities announced that Carriage Gates, the main entrance to Parliament where PC Palmer was stabbed to death, will be closed and pass holders will have to use another entrance to get into work.

The army will also be deployed to guard Parliament.