Here is what we been able to confirm so far:
- Four people have died, including a police officer and one man believed to be the attacker, police said.
- At least 20 other people were injured in the attack, some with “catastrophic” wounds.
- The alleged assailant drove a car into pedestrians on Westminster Bridge before crashing it and then trying to enter the complex, armed with a knife.
- He was shot by armed police inside the security cordon of the Houses of Parliament.
- Police currently believe there was only one attacker, but have locked down the area around Westminster and are searching the area.
Attack at parliament
- Two of the victims are thought to have died on the bridge.
- Several French students were among the injured, the French prime minister, Bernard Cazeneuve, said.
- Three police officers returning from a ceremony were also among those injured on the bridge.
- One woman was rescued from the Thames with serious injuries, after she apparently jumped or fell from the bridge, a spokesman for the Port of London Authority said.
- Minister for counter-terrorism Tobias Ellwood was among those who raced to give first aid to the police officer who later died. Pictures showed him with blood on his face as he administered CPR
- Scotland Yard said the attack in Westminster was being treated “as a terrorist incident until we know otherwise”.
- The House of Commons has been put in lockdown, with many MPs confined to the Commons chamber after parliamentary business was suspended.
- Armed police were searching the Palace of Westminster
- The prime minister, Theresa May, was evacuated from the parliament building within minutes and driven to Downing Street.
- London ambulance service said it was called to Westminster Bridge at 2.40pm, with the first crew arriving within six minutes. It has declared a major incident.
- Both the ambulance service and the Metropolitan police have appealed to the public to call 999 only in a genuine emergency.
- The London Eye, opposite parliament on the other side of Westminster Bridge, is also in lockdown, with some being held inside the attraction’s pods.
- The Thames has been closed to all but emergency vessels between Vauxhall Bridge and Embankment.