(KUNA) -- Police has arrested a militant of an outlawed extremist outfit for his alleged involvement in the killing of a Shiite cleric in Southern Karachi port city, said police Wednesday. Arshaad Khan, member of Al-Qaeda linked Lashkar-i-Jhangvi (LJ) extremist group, was arrested in a raid conducted on Tuesday night in Hyderabad city, about 150 kilometers from Karachi, a police source told KUNA.Allama Hassan Turabi, his nephew Ali Raza and a child were killed last week when a suicide bomber blew himself up outside the clerics house. Three people were also critically wounded. The killing sparked violent protests in the city. Dozens of buses, two banks and a foreign food chain restaurant were set on ablaze by angry Shiite mourners.