By Syed Raza Hassan
KARACHI, Pakistan (Reuters) - Pakistan's Muttahida Qaumi Movement (MQM), the secular party that governs the port city of Karachi, on Tuesday accused the regional paramilitary Pakistan Rangers force of killing another one of its members while in their custody.
MQM accuse the Rangers of having carried out dozens of extra-judicial killings of party members since the force launched a crackdown on crime in Karachi in 2013.
Last year, the U.N. Working Group on Enforced or Involuntary Disappearances referred 55 cases of illegal abductions of MQM workers to the government, concluding a "pattern of specific targeting" of the MQM by Rangers.
MQM said Aftab Husain, a prominent party activist and an aide to Farooq Sattar, MQM leader in the National Assembly, was arrested at his house on May 1 and died two days later.
The Rangers, who answer to the Ministry of Interior and to the army, say Husain was "wanted in several criminal cases" and had died of a heart attack.
"During custody he complained of chest pain on Tuesday morning and was rushed to the hospital where he died," the Rangers said in a statement.
MQM have their main support base in Karachi, but law enforcement agencies and many residents accuse the party of racketeering, the abduction, torture and murder of opponents and holding the city to ransom by calling mass strikes at will.
London-based MQM founder and leader Altaf Hussain called for an independent investigation into Husain's death by Pakistan's Supreme Court.
Husain was "extra-judicially killed in Rangers custody", MQM said in statement.
Last year, MQM submitted a list of 46 members it says were killed extra-judicially by Rangers to the office of Prime Minister Nawaz Sharif, calling for the force to be more accountable.
Officials from the Rangers deny this. The government has not said if it would take any action.
(Editing by Drazen Jorgic and Raissa Kasolowsky)