Pakistani security forces have been ordered to shoot on sight in Karachi, after several days of political and ethnic violence in the city have left up to 85 people dead.

Interior Minister Rehman Malik told reporters Friday that dozens of suspects have been detained in connection with the series of targeted killings that have taken place since Monday. At least 34 people died on Thursday alone, after gunmen opened fire on buses.

Police say the killings are part of clashes between political groups in Sindh province, including the Muttahida Qaumi Movement and its rival Awami National Party .

The MQM largely represents the Urdu-speaking community, and until last month was part of the ruling coalition in Sindh. ANP represents ethnic Pashtuns. The groups, along with ruling Pakistan People's Party, are believed to have links to armed groups in the city.

Some 1,000 additional police and paramilitary forces were deployed to Karachi on Friday, with troops ordered to shoot on sight any armed “miscreants” involved in attacks.

Shops were also closed and streets were deserted in the southern port city Friday, as the MQM called for a day of mourning and protest rallies.

MQM leader Raza Haroon said Thursday MQM supporters were being targeted because the party quit the coalition.

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

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