A manhunt has been launched after a bomb was detonated in a terror attack on a packed London Underground train.
Witnesses described scenes of terror and panic as the blast sent a "fireball" and a "wall of flame" through a District line service at Parsons Green station in west London.
Police suspect the explosion was sparked when an improvised explosive device was detonated, and have launched a huge counter-terrorism investigation alongside MI5.
The device is being forensically examined while detectives are scouring CCTV and examining witness statements for potential leads.
London Mayor Sadiq Khan told LBC radio "there is a manhunt under way as we speak", while Scotland Yard said detectives are making "fast-time" inquiries to establish who was responsible, adding that there have been no arrests.
Prime Minister Theresa May condemned the "cowardly attack", saying it involved a device "clearly intended to cause significant harm".