The UK House of Commons sitting has been suspended as witnesses report sounds like gunfire outside. Picture: Victoria Jones/PA via AP

London – An assailant was shot outside the British parliament by armed police, the leader of the House of Commons said on Wednesday after loud bangs were heard and a Reuters photographer saw at least a dozen injured people on a nearby bridge.

A parliamentary official earlier said two people had been shot outside parliament and the building was in lockdown. The House of Commons session was suspended and members of parliament who were in the chamber were told to remain there.

Police said they had been called to an incident at Westminster Bridge, officers were on the scene and it was being treated as a firearms incident.

A Reuters reporter inside the building said medical staff were treating two people inside the gates of the parliamentary estate.

Nearby Westminster underground train station was closed at the request of police.

Photographs by Reuters staffer Toby Melville showed two people lying on Westminster Bridge, bleeding heavily.