Fresh violence has erupted in Pakistan's largest city, with at least 11 people killed Friday.

More than 18 others were wounded in clashes between rival groups in Karachi.

Authorities would not say whether the killings were politically motivated.

Political and ethnic violence has killed at least 100 people in Karachi so far this month. The unrest has escalated since the Muttahida Quami Movement party pulled out of Sindh province's ruling coalition in June.

Police say the killings are part of clashes between the MQM, which largely represents the Urdu-speaking community, and its rival, the Awami National Party , which represent ethnic Pashtuns. Both those parties and the ruling Pakistan People's Party are believed to have links to armed groups in Karachi.

Last week, the Pakistani government deployed additional police and paramilitary forces to the city to help quell the unrest. The previous wave of violence erupted after the head of the PPP in Sindh, Zulfiqar Mirza, called MQM's leaders criminals.

Some 18 million people live in Pakistan's economic hub of Karachi. The city has also been the scene of sectarian violence between Sunni and Shi'ite Muslims, and militant attacks.

The Human Rights Commission of Pakistan says 490 people died in targeted killings in Karachi in the first half of this year.