Islamabad:  At least 11 people, including six policemen, were killed on Saturday in Pakistan's port city of Karachi as the new wave of violence in the metropolis continued for the fourth day, taking the toll to 77.

The policemen were killed when militants attacked their bus in Chakragoth area of the city. Fifty others were injured, said media reports. Two assailants were also killed.

Interior Minister Rehman Malik said the police personnel were hit when they were on their way to conduct a search operation.

Five more people were killed in the metropolis on Saturday, a news channel reported. The victims who belonged to the Lyari area of the city were kidnapped and later killed.

Violence was also witnessed in Orangi, Pak Colony and other areas of the city. In Orangi, an ambulance was attacked, injuring three people, including the driver. In Korangi and Sohrab Goth areas, mini buses were attacked.

The toll in the past four days of violence in the city rose to 77 on Saturday.

Meanwhile, Prime Minister Yousuf Raza Gilani has called for political parties to play their role in curbing the violence in the port city, media reports said.

On Aug 17, the city witnessed firing, grenade and rocket attacks in Tariq road, Soldier Bazaar, Kharadar and Saddar areas.

Sixteen people, including a former lawmaker of the Pakistan Peoples Party were killed, while 20 others were injured.

On Aug 18, 30 people were killed after they were abducted from different parts of the city. Their bodies were recovered from Lyari, Pak Colony, Sher Shah and other areas of the city. Many of the victims had been decapitated.

On Friday, 26 people were killed and 46 others were injured in violence in different parts of the city.