Altaf Hussain, Pakistan's powerful Muttahida Qaumi Movement leader, was arrested on Tuesday in London on charges of money laundering.
Scotland Yard confirmed that a 60-year-old man had been arrested from a North-West London property on charges of money laundering, but declined to disclose the exact identity of the individual for "legal reasons".
Officers were searching "a residential address in north-west London, where a 60-year-old man was detained," police said.
Even as police did not name Hussain, media reports in Pakistan quoting sources said the MQM chief had been arrested on suspicion of money laundering.
Hussain has lived in the UK since 1991, saying his life would be at risk if he returned to Pakistan.
A spokesman for the British high commission was quoted by Dawn News as saying that the UK's consulate in Karachi has been temporarily closed down.
Prime Minister Nawaz Sharif said that the issue of Hussain's arrest was of an extremely sensitive nature and the government would take all legal angles into account.
The prime minister directed that the parliament be taken into confidence over the matter.
Hussain had been ill for some time and was scheduled to be shifted to a hospital on Tuesday when the police arrived at his residence, MQM's Nadeem Nusrat said while addressing media representatives via telephone from London.
Nusrat advised all party members inside and outside Pakistan to control their emotions and not do anything that may go against the teachings of their leader.
Nusrat insisted that Hussain was not under arrest but at home.
Image: MQM leader Altaf Hussain
