Police have raided addresses in the aftermath of Wednesday’s fatal terror attack in Westminster, London, as officers sought individuals connected to the suspected killer.

Metropolitan Police have yet to name or in any way identify Wednesday’s killer, who drove a powerful hired car along the pavement on Westminster Bridge, mowing down around 20 pedestrians before crashing and disembarking. On foot and armed with a large knife, the individual then rushed Palace Yard, the vehicle entrance to the Palace of Westminster, and stabbed an unarmed police officer to death.

Just moments later, the assailant was shot fatally by armed protection officers stationed at the palace.

Three victims have been confirmed by police to have died. The killer himself takes the death toll to four. Total wounded is thought to be around 40. Of those, 29 were hospitalised and some were described as being in critical condition.

The slain police officer, 49-year-old Police Constable Keith Palmer, was stabbed just yards from where government minister and close confidant of Margaret Thatcher Airey Neave was killed by a terrorist bomb in 1979.

Overnight raids hit six addresses in London and Birmingham, the United Kingdom’s first and second cities. Seven individuals believed to be connected with Wednesday’s killer — who police said was motivated by “international terrorism” — were arrested.

West Midlands Police, who performed the raids in central Birmingham, said in a statement:

“Overnight our colleagues from the Metropolitan Police have searched a number of addresses across the country and have made a number of arrests in connection with the incident, including addresses in Birmingham.

“The arrests and searches were intelligence led and there was no immediate risk to public safety.

“We would like to reassure our communities that we have extra officers out on patrol throughout the next few days to offer reassurance and address any concerns you may have. We are keen to stress that this additional security is not based on any new or emerging intelligence.”

Although the identity of the terrorist has not been made public by Scotland Yard, a police spokesman said he had been positively identified and was previously known to police.