Rescue services worked through the night to put out fires at several markets, set by angry mobs after an attacker blew himself up Monday among a procession of Shiite Muslims commemorating the death of the Prophet Mohammed's grandson, Imam Hussein.
Sagheer Ahmad, health minister in the southern province of Sindh, of which Karachi is the capital, told Samaa television channel that the death toll had hit 43 after several people succumbed to their injuries.
Doctors at the city's two main hospitals said more than 100 wounded people were brought to the facilities but they included some with minor injuries caused by shrapnel.
Many severed limbs and body parts were also received.
The provincial government announced a holiday on Tuesday to mourn the killings, and appealed for calm. Offices, schools and commercial centres remained closed throughout Karachi, while public transport largely kept off the roads.
Police officials said "the situation is calm but tense."
Angry Shiite Muslims destroyed dozens of vehicles, including police cars and ambulances, following the suicide attack that came despite the deployment of thousands of security force personnel to protect the annual processions during the holy month of Muharram.
But merchants said the market fires were sabotage and demanded the government expose the unscrupulous elements behind them.
"These fires have caused damage of more than 2.5 billion rupees (30 million dollars) and it will take years to rehabilitate the markets," Zakaria Usman, vice-president of Pakistan's traders group, told the Geo News television channel.
Interior Minister Rehman Malik also doubted that the arson attacks were carried out by enraged Shiite Muslims, arguing that fires started at multiple locations within minutes.
"It appears to be a planned scheme," he told reporters in Karachi.
Around 500 shops are believed to have been completely gutted, and flames could be seen rising from some buildings until Tuesday afternoon.
Firefighters were called from Karachi's neighbouring Hyderabad district to assist the local firemen.
No group has yet claimed responsibility for the bombing. Malik blamed a "triangular syndicate" of Taliban, al-Qaeda and Sunni militant groups for the carnage.
Monday's suicide attack was the latest in a series of bombings that began in October, when the military launched a major offensive in the Taliban heartland of South Waziristan near the Afghan border.
More than 550 people have been reported killed in the offensive, mostly in the restive North-West Frontier Province, located near the tribal badlands.
The assault on the procession in Karachi drew condemnation from all sects and political parties, with leaders describing it as an attempt to pitch Shiites against Sunnis.
Shiite Muslims account for 20 per cent of Pakistan's population of nearly 170 million.
Separately, Pakistani army claimed on Tuesday that it had killed a militant commander in north-western Swat valley, where the country's armed forces have defeated Taliban rebels in an operation that was launched early this year.
Security forces conducted a search operation near the Charbagh area and killed Abu Zar, a wanted terrorist commander, the military said in a statement, adding that Zar was an explosives expert who planned attacks against the military.
"Two other terrorists were also apprehended with a cache of arms and ammunition," the statement said. dpa yam ns tl im se ms
- Deutsche Presse Agentur
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