Syed Raza Haider, a leader of the MQM party, was shot Monday evening at a mosque where he was attending the funeral of a relative, according to Rafiq Gul, Karachi's deputy superintendent of police. The gunman also killed the politician's bodyguard.
Gul said the Haider's death triggered political and ethnic violence in the city, as mobs set fire to vehicles and gunfire erupted.
Gul said 48 vehicles, eight shops and several gas stations were set ablaze in the mayhem.
The MQM is part of the ruling coalition backing President Asif Ali Zardari's Pakistan People's Party.