An assailant stabbed a policeman and was shot by police just outside Britain's parliament building in London on Wednesday (March 22) in what police described as a "terrorist incident".

Amid confusing scenes, it appeared the incident may have unfolded in several locations, including on the nearby Westminster bridge where eyewitnesses said a car had crashed into pedestrians.

Two people died in the incident, according to Sky News, but the total number of casualties was unclear.

The incident took place on the first anniversary of attacks by Islamist militants that killed 32 people in Brussels.