A worker of the Muttahida Qaumi Movement (MQM) died in the custody of Pak Colony police on Monday under questionable circumstances.

"Waseem alias Raja committed suicide while in custody by hanging himself using a piece of cloth," claimed Karachi West SSP Nasir Aftab.

The police officer added that a policeman heard a "strange voice" coming from the lock-up late Sunday night. He rushed towards the lock-up, only to find Waseem hanging.

Hospital officials, on the condition of anonymity, told Dawn the police's version of the story does not match with the results of the post-mortem report.

"There are no signs of strangulation on the neck of the deceased," he said. The post-mortem report has not yet been released.

Police say the MQM worker was detained on Sunday after he was caught carrying an illegal weapon.

MQM-London has condemned the incident. Party leader Nadeem Nusrat said in a statement that Waseem was "killed extra-judicially", alleging that at least 67 of its party workers have been murdered like that.

Separately, the MQM-Pakistan leader Dr Farooq Sattar confirmed Waseem, a party worker in Orangi Town of Karachi, had died in custody.