Here are the latest updates:
Police say attack is linked to Islamic extremism
At least eight people have been arrested after overnight raids in London and Birmingham
Four people were killed in the attack and 40 injured, some seriously
Terrorist among those dead after being shot by police
Killed police officer identified as PC Keith Palmer
Seven others remain critically injured
Police have asked for the identity of the terrorist not to be revealed by the media
Parliament to meet again as normal this morning
Video captures moment police shoot dead terrorist
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Armed police have launched a late-night raid on an address in Birmingham.
West Midlands Police referred inquiries about the operation on Hagley Road to the Metropolitan Police, who refused to say whether it was connected with Wednesday’s attack in Westminster.
But a witness who works nearby told the Press Association: “The man from London lived here.”
Officers stormed a second-floor flat above a row of shops on Hagley Road at around 11pm, the witness said.
He added: “They came and arrested three men.”
One of the flat’s windows was covered in cardboard, with non-uniformed officers spotted taking pieces of equipment into the property.
As he was describing the events, the witness was interrupted by a police officer, who had been guarding the scene.
He had his details taken and was convinced to go to a police station with another officer.