Nearly a week of political and ethnic violence has killed at least 91 people in Pakistan's largest city, Karachi.

Police say the bodies of at least 11 people who were shot or tortured to death have been brought to government hospitals in the southern port city since Sunday.

Pakistani Prime Minister Yousuf Raza Gilani traveled to Karachi, the capital of Sindh province, Monday and held talks with provincial government officials. Mr. Gilani said strict action should be taken against those responsible for the violence.

In Pakistan's northwest, local security officials said a U.S. drone strike killed four suspected militants near the town of Mir Ali in the North Waziristan tribal region — a known refuge for Taliban and al-Qaida-linked militants.

Also Monday, authorities said gunmen in the southwestern province of Baluchistan set fire to at least 18 trucks carrying fuel for NATO forces in neighboring Afghanistan. There were no reported casualties.

And the Committee to Protect Journalists said three journalists working for Khyber TV were attacked in broad daylight in the northwestern city of Peshawar Monday. Two others managed to escape.

Earlier this year, the New York-based group said Pakistan was the deadliest nation in the world for journalists.

Hundreds of people have been killed in Karachi in recent months, in one of the worst waves of unrest there in years. Many of the killings are blamed on ethnic gangs linked to rival political factions such as the majority Urdu-speaking Muttahida Qaumi Movement and the Awami National Party of Pashtun migrants.