Police officer shot dead inside London police station

London's Metropolitan Police force said the officer was shot at the Croydon Custody Centre in the south of the city just after 2am. Photo / Supplied

A British police officer was shot dead inside a London police station early Friday while detaining a suspect, who also sustained a gunshot wound.

London's Metropolitan Police force said the officer was shot at the Croydon Custody Centre in the south of the city just after 2am. He was taken to a local hospital where he was pronounced dead.

The 23-year-old man being detained is in critical condition in a hospital.

My deepest condolences go to the family, friends and colleagues of the police officer who was killed in Croydon last night.

We owe a huge debt to those who risk their own lives to keep us safe.

— Boris Johnson (@BorisJohnson) September 25, 2020

The force said no police weapons were fired.

It is rare for police officers to be shot and killed in the UK, which has strict firearms laws.

Prime Minister Boris Johnson and other senior politicians expressed shock at Friday's death.

"We owe a huge debt to those who risk their own lives to keep us safe," Johnson said.

London Mayor Sadiq Khan said, "My heart goes out to the family of this brave officer, who has paid the ultimate price for helping to keep Londoners safe."

"When a colleague dies in the line of duty the shockwaves and sadness reverberates throughout the Met and our communities," said Metropolitan Police Commissioner Cressida Dick.

"Policing is a family, within London and nationally, and we will all deeply mourn our colleague."

The force has launched a murder inquiry and the independent police watchdog is also investigating.

The last London police officer killed in the line of duty was Constable Keith Palmer, who was stabbed to death in March 2017 during a vehicle and knife attack outside Parliament.

- AP