By Toby Melville | LONDON
A policeman was stabbed, an assailant shot and several people injured on Wednesday close to Britain's Houses of Parliament in what police said they were treating as a terrorist incident.
Reuters reporters inside the building heard loud bangs and shortly afterwards a Reuters photographer said he saw at least a dozen people injured on Westminster Bridge, next to parliament.
His photographs showed people lying on the ground, some of them bleeding heavily and one apparently under a bus. The number of casualties was unclear.
"Officers - including firearms officers - remain on the scene and we are treating this as a terrorist incident until we know otherwise," London's Metropolitan Police said in a statement.
The House of Commons, which was in session at the time, was immediately suspended and lawmakers were asked to stay inside.
Prime Minister Theresa May was safe after the incident, a spokesman for her office said. He declined to say where May was when the attack took place.
The leader of the House, David Lidington, said in the chamber that an assailant who stabbed a policeman had been shot by police.
An ambulance helicopter landed on Parliament Square, just outside the building.
The BBC said police believed there was a suspect vehicle outside parliament but police did not immediately confirm that report.