Shock after the explosion at Parsons Green. | Reuters

An explosion on a tube train at Parsons Green station this morning has left a number of people with burns. Twenty-two people have been taken to hospital with what are described as flash burns. None of the injured is said to be in a serious condition.

The London Ambulance Service was called at 08.20 this morning because of an incident at the station, which is on the District Line to Wimbledon. Witnesses said that people were screaming and being trampled as they tried to escape. There was a bang and then a wall of flames when the explosion occurred.

Armed police were deployed. Deputy Assistant Commissioner Neil Basu, the senior national coordinator for counter-terrorism policing, declared it a terrorist incident. Metropolitan Police Assistant Commissioner Mark Rowley said the explosion was caused by an improvised explosive device with a timer. 

London mayor Sadiq Khan has said: "The Metropolitan Police have confirmed that the explosion on a train at Parsons Green Station this morning is being treated as terrorism. Our city utterly condemns the hideous individuals who attempt to use terror to harm us and destroy our way of life. As London has proven again and again, we will never be intimidated or defeated by terrorism."