Four killed in attack at UK Parliament

Four people, including an assailant and a police officer, were killed today in an attack at the Houses of Parliament that authorities say was an act of terrorism.

Ministers of Parliament were locked in after police shot and killed a man who reportedly ran at the gates by Parliament square and stabbed an officer. Moments earlier, a car had run five people over on nearby Westminster Bridge, leaving at least two dead and twenty injured.

Prime Minister Theresa May is to chair an emergency meeting of ministers today, writes the BBC.

BBC Radio 5 reports that "around three shots" were heard.

Update: the BBC posted a map of the area and the events as reported, with a detailed eyewitness report.

Press Association political editor Andrew Woodcock witnessed the scenes unfolding from his office window overlooking New Palace Yard.
"I heard shouts and screams from outside and looked out, and there was a group of maybe 40 or 50 people running round the corner from Bridge Street into Parliament Square. They appeared to be running away from something. As the group arrived at the Carriage Gates, where policemen are posted at the security entrance, a man suddenly ran out of the crowd and into the yard. He seemed to be holding up a long kitchen knife. I heard what sounded like shots – I think about three of them – and then the next thing I knew there were two people lying on the ground and others running to help them.