A spokesman for the British High Commission (embassy) said the two diplomats, a man and woman, suffered a "vicious and unprovoked attack" by several men as they were walking home at night in a posh district of the Pakistani capital.

The attack took place in the early hours of Sunday morning, and the two victims required medical treatment, he said. A motive for the attack had not been ascertained, he said.

Police confirmed Saad Ali Khan, Khan's son-in-law, was being held.