Pakistan's southern port city of Karachi has shut down for a day of mourning, following political violence that has killed at least 56 people since Saturday.
Security forces patrolled the city Wednesday, with businesses closed and public transportation suspended in most areas.
Pakistani Prime Minister Yousuf Raza Gilani said no decision had been made to deploy the army to Karachi, and that civilian authorities were capable of controlling the situation.
Officials say at least 55 suspects have been detained in connection with the violence. In the worst single attack, gunmen killed 11 people at a market on Tuesday.
The killings coincide with a by-election Sunday to replace a lawmaker killed earlier this year.
Provincial lawmaker Raza Haider from the Muttahida Quami Movement was gunned down in Karachi in August.
MQM, which largely represents the Urdu-speaking community, and the rival Awami National Party, representing ethnic Pashtuns, blame each other for the violence.
Haider's assassination in August sparked four days of violence that killed at least 85 people.
Karachi, the largest city in Pakistan and its commercial hub, has long been plagued by ethnic and politically motivated killings.
In other violence Wednesday, military officials say a roadside bomb killed at least two Pakistani soldiers and wounded three others in the northwestern Khyber tribal region.
Some information for this report was provided by AFP and Reuters.