Article published on the 2008-12-01 Latest update 2008-12-01 15:24 TU
Troops were authorised to use guns to quell the violence, after rioters set shops and houses on fire in the Orangi Town district. Schools and petrol stations were closed Monday, for fear of further violence.
Officials blame two parties, the Muttahida Qaumi Movement (MQM) and the Awami National Party (ANP), but their leaders deny involvement.
The MQM, which leads the city's ruling coalition, has support among Urdu-speakers who have come to the city from India, mostly after the partition of the subcontinent in the 1940s. The ANP, which is also in the ruling coalition, is a Pashtun-nationalist party, which started in the north-west and has support among Pashtun immigrants to Karachi.
Prime Minister Yousuf Raza Gilani, whose People's Party has often clashed with the MQM, ordered provincial authorities to take "strict action", saying "no one will be allowed to put at risk the lives and property of the people".
In the North-West Frontier Province ten people were killed and 50 injured when a suicide bomber blew up his explosives-laden car near a security checkpoint in the town of Mingora, according to officials.
All the dead were civilians, according to police, as were all but one of the injured.
In two separate clashes outside the town, two Islamist fighters and one soldier were killed and several others injured.
The Swat Valley, where the clashes took place, has been a battleground since radical cleric Maulana Fazlullah, who has links to the Pakistani Taliban, launched a violent campaign for the introduction of Islamic Sharia law there.
2008-11-22 11:11 TU