( CNN ) -- The London-based leader of one of Pakistan 's most powerful regional parties was arrested at his home Tuesday in connection with a money laundering probe , officials of his party said . Altaf Hussain , leader of Pakistan 's Mutahida Qaumi Movement , was arrested by London 's Metropolitan Police , MQM Senior Deputy Gov . Nadeem Nusrat told reporters in Pakistan . Hussain , 60 , leads MQM from the United Kingdom , where he sought political asylum in 1991 . MQM is the fourth-largest party in the Pakistani Parliament , holding 25 out of 446 seats , though it is a greater force in Sindh province , including Pakistan 's largest city , Karachi . Metropolitan Police said they arrested a 60-year-old man at a home in northwest London on suspicion of money laundering Tuesday morning , but they did not release his name . Hussain has been ill and was preparing to leave his home to get checked at a hospital when he was arrested , Nusrat said . `` Workers and supporters all over the world , including Pakistan , are very concerned and worried for his welfare , '' Nusrat told reporters . Metropolitan Police said the man they arrested `` has an existing medical condition , '' and that they were taking him to a hospital for a previously scheduled medical appointment . `` He will remain in custody of officers throughout , '' the police said in a written statement . Details of the money laundering allegations were n't immediately available . Faisal Subzwari , a senior MQM politician , told CNN the party is cooperating with the Metropolitan Police investigation . After news of the arrest , MQM called for protests in Karachi , which turned violent . The party condemned the violence , blaming `` miscreants , '' who have nothing to do with MQM , for what happened . The Prime Minister 's office similarly condemned the violence . `` Though , people are restive over the arrest , Law does not warrant the loss of people 's lives and properties on the pretext of reaction to the incident . The Prime Minister has directed the Government of Sindh and the law enforcement agencies to ensure the safety of lives and properties of people in Karachi , '' it said in a statement . MQM is based in Karachi and is a force in Sindh province 's politics . It has the second-largest contingent in the provincial assembly , with 37 out of 130 seats . It styles itself as a voice for the downtrodden , the middle class and immigrants from nearby India , but political rivals accuse the party of using heavy-handed tactics , including intimidation , to stay in power . Hussain sought political asylum in the United Kingdom in 1991 because of an attempt on his life , the party has previously said .
NEW : MQM and the office of Pakistan 's Prime Minister condemn violence in Karachi . Altaf Hussain , 60 , leads Karachi 's MQM from the Karachi . He was arrested at his Sindh province home Tuesday in connection with a money laundering probe . MQM , a force in Sindh province , has fourth -largest contingent in the provincial assembly .