London, England (CNN) -- Pakistani politician Imran Farooq was killed Thursday in London, a spokesman for his party told CNN.
Farooq was a prominent member of the Muttahida Quami Movement. News of his killing was made public Thursday evening, said Mohammad Anwar, a member of the party's Central Coordination Committee.
He led the committee, which is the party's highest decision-making body, Anwar said. Farooq also led international relations and human-rights affairs for MQM, Anwar said from the party's London office.
Farooq lived in northwest London, near the party's office in Green Lane, Edgware, he said.
Police said they were called to Green Lane, Edgware, shortly before 5:30 p.m. after reports of a serious assault.
"On arrival, officers found an Asian man, aged 50, with stab wounds and head injuries," Metropolitan Police said in a statement. Paramedics treated him, but he was pronounced dead at 6:35 p.m., police said.
Police are awaiting formal identification, according to the statement. No arrests have yet been made.
Anwar said party leaders in Karachi learned of the news by speaking with Farooq's parents.
"It's very sad," Anwar said. "We thought in London he was safe that no one could bring harm to any party members in London."
He called Farooq's death an "irreparable loss for the party."
"Dr. Farooq's sacrifice has made us stronger to bring change back in Pakistan."
Farooq moved to London in September 1992 after concluding his "life and liberty were at risk back home," Anwar said.
The party was fighting the military, which has bankrupted the country, Anwar said, "because the ruling elite have fattened themselves and made the country poor as a result of rampant corruption."
Shortly after the announcement of the killing, MQM announced 10 days of mourning, MQM's Deputy Convenor Dr. Farooq Satar told reporters in Karachi.
Satar, who is head of the party in Pakistan, said party political activities would be suspended during the mourning period.
MQM is a part of coalition government led by President Asif Ali Zardari's Pakistan People's Party in central and southern Sindh province. MQM is a liberal party with a stronghold in the southern city of Karachi.
"All the party workers are in deep shock and," Satar said.
News channels broadcast video of Altaf Hussain, the leader of MQM who is also on self-exile in London, crying over the news.
"How will I bear this shock," he said about Farooq's death. "He sacrificed his life for revolution."
Violence erupted in Karachi Friday morning, police told CNN.
Amir Shakeel Butt, a Karachi police official, said angry people set afire four vehicles and a shop in the town of Clifton in Karachi's southern zone. No casualties were reported, he said.
CNN's Katy Byron contributed to this story.