MQM-London leader Mohammad Anwar passed away on Friday at a London hospital where he was being treated for cancer.
His nephew Imbisat Mallick confirmed the news on Twitter.
"With our deepest sorrow we inform you, our beloved Mohammad Anwar passed away peacefully, surrounded by his family, today after bravely battling a lethal cancer," he tweeted.
Anwar lived in London and was part of the MQM since 1989. His association with party chief Altaf Hussain spans two decades. He was also a member of the MQM’s coordination committee, also known as Rabita Committee.
Anwar was nominated in several cases including the Imran Farooq murder case. He was also probed in a money laundering case by the London Metropolitan Police.
In 2015, he was sacked from the MQM Rabita Committee due to his continued illness, which had often caused him to "remain absent from crucial meetings".
In the same year, Anwar was named in a sedition case lodged in Karachi. The case was registered a day after an antiterrorism court declared MQM chief Altaf Hussain a proclaimed offender in a case of criminal intimidation.