May chairs emergency meeting after attack

Prime Minister Theresa May has chaired a meeting of the Government's emergency Cobra committee

Prime Minister Theresa May has chaired a meeting of the Government's emergency Cobra committee. (AAP)

to discuss the immediate response to the bloody incident at the Palace of Westminster.

The 45-minute meeting brought together senior ministers as well as senior police officers, representatives of the security agencies and London Mayor Sadiq Khan.

Mrs May ordered flags to be lowered to half mast over Downing Street as a mark of respect to the innocent people who lost their lives at Westminster.

The meeting in Whitehall was addressed by Metropolitan Police Assistant Commissioner Mark Rowley, Britain's most senior anti-terrorist police officer.