London (CNN) An area around the Houses of Parliament and Westminster Bridge in central London has been locked down Wednesday as the city's Metropolitan Police deal with what they are treating as a terrorist incident. Here's what you need to know:• At least three people, including a police officer protecting Parliament, have been killed, and at least 20 injured, Met Police Acting Deputy Commissioner Mark Rowley tells reporters. • The attack started when a car was driven over Westminster Bridge toward the Houses of Parliament, hitting and injuring a number of members of the public and three police officers on their way back from a commendation ceremony, Rowley said. The car then crashed near Parliament and at least one man, armed with a knife, continued the attack by trying to enter Parliament. JUST WATCHED Crashed car smokes outside Parliament Replay More Videos ... MUST WATCH Crashed car smokes outside Parliament 00:26• London Ambulance Service said at least 10 people were treated on Westminster Bridge, where the attack started.

Source: CNN March 22, 2017 17:54 UTC