A policeman was stabbed, an assailant shot and several people injured on Wednesday (March 22) 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.

The BBC said police believed there was a suspect vehicle outside parliament but police did not immediately confirm that report.

Amid confusing scenes, it appeared the incident may have unfolded in several locations, including on the busy Westminster Bridge where tourists take pictures of Big Ben and other attractions.