Islamabad, Pakistan (CNN) -- At least 42 people died and another 145 were wounded in a massive car bombing Sunday in the large Pakistani seaport city of Karachi, authorities said.
The toll could rise as rescue workers continued to recover bodies early Monday, said Syed Hashim Raza Zaidi, the top government official in Karachi.
The blast apparently targeted Shiite Muslims who lived in buildings surrounding where the vehicle, loaded with 150 kilograms of explosives, was parked, according to senior Karachi police official Rao Anwar Ahmed.
A timing device triggered the explosion next to a market in Karachi's Abbas town, Ahmed said.
Two explosions were initially reported, but the second blast has been attributed to a pipe that exploded as a result of the bombing, he added.
As of about midnight Sunday, no militant groups were known to have claimed responsibility, said Zaidi.
Pakistan's Prime Minister Raja Pervez Ashraf and President Asif Ali Zardari both immediately condemned the attack.
"Expressing sympathies with the bereaved families, the president directed the authorities concerned to ensure that the best medical treatment was provided to the injured," a statement from Zardari said.
Pakistani has seen several such deadly attacks in recent years, including one last month that struck a crowded marketplace on the outskirts of Quetta that killed at least 89 people and wounded at least 180 others. That blast followed a January day of bomb attacks targeting Shiites in Quetta that left at least 85 people dead.
On February 1, a suicide bomber detonated his explosives near a marketplace in the northern Pakistan city of Hangu near the Afghanistan border, killing at least 23 people.
Such violence is a common problem in the volatile Khyber Pakhtunkhwa province, which, like Quetta's home province of Balochistan, borders Afghanistan.
Karachi, meanwhile, is some 1,350 kilometers (840 miles) south of Hangu and 800 kilometers (about 500 miles) from Quetta on Pakistan's southern coast. Situated along the Arabian Sea, it is the South Asian country's financial center and its most populated city.
Still, despite its distance from Pakistan's tumultuous western border areas, Karachi has not been entirely immune to violence.
In February 2010, for instance, at least 18 people died in blasts targeting a bus full of Shiite religious observers and another in front of a hospital. And in late 2009, a suicide bombing targeting a Shiite procession moving through Karachi killed at least 40 people.