KARACHI, Pakistan -- Gunmen opened fire on two bus and waged street battles in Pakistan's largest city Thursday, killing at least 22 people as part of a spate of violence that has claimed 49 lives in three days, officials said.
It was some of the worst strife so far this year in Karachi, a city of 18 million that has long been a hotbed of crime and clashes -- much of it linked to ethnic, sectarian and political divisions. Police had no immediate comment on the possible motives for the latest killings.
At least 22 people were killed Thursday, said Sharfuddin Memon, a security adviser for Sindh province, where Karachi is located. Ten of the victims died when gunmen targeted two buses, he said.
Memon said 27 other people were killed in sporadic shootings Tuesday and Wednesday. He feared the toll could go further high as more violence was reported.
Some Pakistani television reporters wore bulletproof vests as they filed their reports. Live TV footage showed gunmen in makeshift bunkers and exchanging shots.
Karachi's most powerful political party, the Muttahida Qaumi Movement, or MQM, threatened to call for a citywide strike unless the federal government brings the bloodshed under control.
"We reserve a right to give a strike call," said the party's lawmaker, Raza Haroon.
The MQM is suspected of links to some of the armed gangs in the city, as are some rival political parties such as President Asif Ali Zardari's Pakistan People's party and its ally, Awami National Party, a Pashtun origin liberal party.
Irshad Bokhari, another Karachi official, said trucking companies took their vehicles off the road and gas stations were shut down amid the mayhem.
An Associated Press reporter saw roads that were nearly deserted.
"We are kind of imprisoned in our own houses," said a resident, Adeel Anwar.