She said said her government was in close contact with counterparts in all the countries affected.Meanwhile, eight people have been arrested in raids in London, Birmingham and elsewhere linked to the attack.Mark Rowley, the Metropolitan Police’s senior anti-terror officer, earlier said six addresses were raided overnight.

Mr Rowley said the death toll from the attack was four, not five.

The dead were: police constable Keith Palmer; Aysha Frade, “a highly regarded and loved” member of staff at DLD College London and a man in his mid 50s who were both mowed down as the terrorist sped across Westminster Bridge in his car; and the attacker himself.

Mr Rowley said 29 people had been treated in hospital with seven people in a critical condition.

Mr Rowley said it was still his belief the attacker worked alone and was inspired by “international terrorism”, adding that there was no specific information to suggest any further threat to the public.

Paramedics give first aid to man who stabbed to death a policeman in London yesterday

A man who witnessed a raid on an address in Birmingham overnight 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.

Parliament sitting as normal despite attack

A moment's silence in the House of Commons

Both the House of Commons and the House of Lords are sitting at their normal times today, in a show of defiance in the wake of the attack.

The House of Commons chamber observed a minute’s silence at the start of proceedings.

Police officers also marked the silence standing outside the headquarters of London’s Metropolitan Police nearby.