LONDON: A British police officer was shot dead early Friday morning by a man believed to have then turned the gun on himself, Scotland Yard said, the first officer to be killed by gunfire while on duty in over eight years.

London's Metropolitan Police Service launched a murder investigation following the shooting by a 23-year-old suspect being detained at Croydon Custody Centre in the south of the British capital at around 2:15am (0115 GMT).

Media reports suggested that the suspect may not have been fully searched prior to entering the facility.

The officer, said to be "a long-serving sergeant", was taken by an air ambulance to a south London hospital where medical staff "did everything they could to save his life", the force's Commissioner Cressida Dick said in a statement.