Police have arrested a prominent Pakistani politician in London. The Metropolitan police said a man in his 60s had been arrested over speeches linked to the Muttahida Qaumi Movement (MQM) movement in Pakistan. The MQM said its founder Altaf Hussain had been “taken for an interview at a London police station”.

Hussain has lived in self-imposed exile in the UK for decades, having sought political asylum in 1992 and later taken British citizenship, but he has continued to play a long-distance role in Pakistani politics. The MQM has been particularly influential in the port city of Karachi, Pakistan’s economic hub, with Hussain broadcasting speeches to supporters from the UK.

The investigation that led to his arrest on Tuesday was led by the Met’s counter-terrorism command. The Met said the inquiry was “focused on a speech broadcast in August 2016 by an individual associated with the MQM movement in Pakistan as well as other speeches previously broadcast by the same person”.

Officers searched an address in north-west London where Hussain was detained and a separate commercial address in the same area. The Met added: “Throughout the investigation, officers have been liaising with Pakistani authorities in relation to our ongoing enquiries.”

The MQM said in a statement it was “a democratic political party and has a firm faith on the British legal system”. It could not immediately be reached for further comment.

Rival politicians in Pakistan have been urging UK authorities to arrest Hussain for many years, alleging that the MQM has shown a readiness to use violence to fight for political power. Critics include Imran Khan, the cricketer turned prime minister, who in 2007 presented a dossier to No 10 urging the government to have Hussain arrested and prosecuted under counter-terrorism laws.

The MQM vehemently rejected Khan’s allegations at the time. One of Hussain’s advisers told the Guardian the MQM was itself a victim of political violence because of its secular beliefs and refusal to compromise with radical Islamists.

Hussain founded the MQM in the 1980s to defend the interests of Muhajirs, the Urdu-speaking descendants of Muslims who moved from India to Pakistan during partition in 1947. Its political strongholds are urban Karachi and Hyderabad.