Police arrested five men in a dawn raid after receiving information about a plot to harm the Pope.
Officers from Scotland Yard conducted raids across London at 5.45am. The men, aged 26, 27, 36, 40 and 50, are being detained under the Terrorism Act 2000.
Despite the threat, the Pope's itinerary has not changed. A spokesman for the Metropolitan Police said:
Today's arrests were made after police received information. Following initial inquiries by detectives, a decision was made to arrest the five men.
Following today's arrests the policing arrangements for the papal visit were reviewed and we are satisfied that our current policing plan remains appropriate.
UPDATE: A statement released by Westminster City Council revealed that the men worked for a private contractor used by the council.
Sources told the Guardian that the men are Muslims and that some of them are Algerian.