|Around 50 people have been killed in Karachi since Saturday when violence erupted ahead of a by-election [AFP]
At least 32 people have been killed in shootings in Pakistan's southern city of Karachi, police have said.
In the deadliest attack on Tuesday, at least 13 people were shot dead when six armed men on motorbikes opened fire in the Shershah Kabari market.
"The attackers came on motorcycles and started indiscriminate firing," Raja Riyasat, a police official, told the AFP news agency.
Several others were injured and Arif Razzaq, a second police official, said the death toll may rise as some of the wounded were in critical condition.
Al Jazeera's Kamal Hyder, reporting from the Pakistani capital, Islamabad, said the scene of the attack was a scrap market normally frequented by labourers from other parts of the country.
"This would have been a busy area because in Pakistan, scrap dealers make a lot of money," he said. "It's a country where everyone cannot afford to buy brand new automobile parts."
He said sporadic gunfights were ongoing in different parts of the city and had resulted 19 more deaths.
About 60 people have been killed in Karachi since Saturday when violence erupted ahead of a by-election to replace a provincial legislator murdered in August.
It was not clear whether Tuesday's attacks were related to that violence.
"The gravity of violence is high, as 1000 people have been killed during the past year," Amir Latif, the bureau chief of Pakistan's largest independent wire service, Online News Network, told Al Jazeera.
"Ethnic violence is increasing with every passing day ... The city is still burning."
Our correspondent said the recent unrest stemmed from a political power struggle.
"For the last few months, various political parties have been battling for control of Karachi.
"The Awami National Party and MQM [Muttahida Qaumi Movement] are fighting what appears to be a turf war," he said. The Awami National Party is MQM's main rival for political posts and control of the city.
"The people of Karachi have been held hostage by these political groups."
The MQM, which is the dominant political force in Karachi, has stepped up pressure on the government to stem the last days' violence, saying its workers were among those killed.
Some sources said the MQM threatened over the weekend to pull out of the federal coalition government with the Pakistan People's Party to protest the violence.
The move, which party sources say was put "on hold" on assurances of strong action to contain the violence, could lead to the government losing its National Assembly majority, or even its downfall if the MQM sides with the opposition.
Karachi has long been plagued by political and ethnic violence and there is concern that the city is being used as a haven for the Taliban. Some violence in the city is also linked to criminal gangs.
At the same time, Karachi is the commercial capital of Pakistan. It generates 68 per cent of the government's revenue and 25 per cent of Pakistan's gross domestic product.
Source: Al Jazeera and agencies