British police on Saturday said they had evacuated Trafalgar Square in central London before an "incident" was concluded. 

"This was investigated and after police took action we have no further concern. This was not terrorism-related," police said on Twitter. 

A police spokesman said earlier lots of checks were being carried out in the area, a short distance from where a concert is to be staged outside Buckingham Palace later in the day.

(With input from Reuters)