British police said on Saturday they had evacuated London's Trafalgar Square, close to where celebrations are taking place later to mark Queen Elizabeth's Platinum Jubilee.
It was understood that a suspicious item was found near the area which was evacuated before the controlled explosion of the item.
"The incident has now been concluded and the square will reopen in due course," police said on Twitter.
A police spokesman said earlier that lots of checks were being carried out in the area, which is a short distance from where a concert is to be staged outside Buckingham Palace later in the day.
He said the incident was believed to have involved a suspicious package.
