Television channels showed footage of unrest throughout the day in Lyari area of Sindh`s provincial capital, a stronghold of the PPP, with repeated clashes between the police and the residents.
Footage showed police firing teargas shells and using water cannons to control mobs which pelted stones and petrol bombs at law enforcement agencies in Pakistan`s most populous city.
Two people were killed and some 20 injured during the day in clashes, rescue officials and police said. The two people killed were identified as Ali, a member of the People`s Aman Committee and a local Pakistan People`s Party (PPP) leader Hassan Baloch.
Baloch was reportedly standing outside his house when he was killed as a result of police firing. Police said protesters threw hand grenades at security forces while armed men took positions on buildings to fire at them.
Violence has continued to rock Karachi since last week in which over 20 people have been killed and the normal life disrupted.
The fresh round of clashes and violence began in Lyari yesterday over the killing of Saqib Pathan, an activist of the banned Aman Committee allegedly by officials of the Crime Investigation Department (CID).
The Sindh government has ordered an inquiry into the murder.
The violence has been linked to ethnic tensions between the Mohajirs, represented by the Mutihida Qaumi Movement (MQM), and Pashtun migrants from Pakistan`s northwest affiliated to the Awami National Party (ANP). Last October, over 100 people were killed in one week alone ethnic and political unrest.