KARACHI, Pakistan (AP) -- Members of Pakistan's Shiite community were digging Monday through the rubble of a massive car bombing in Karachi looking for loved ones as the death toll from the blast the day before reached 45, a Pakistani doctor said.
The explosion on Sunday evening targeted members of the minority sect leaving a mosque in this port city, and underlined the increasing threat faced by Shiites as Sunni militant groups target them in ever-bolder attacks.
At least 146 people were also wounded in the explosion and 32 of them remain in serious condition, said Pakistani surgeon, Jalil Qadir.
There was no immediate claim of responsibility but Sunni militant groups who do not consider Shiites to be true Muslims have carried out such attacks in the past.
This was the third mass casualty attack since the beginning of the year against Shiites. The first two killed nearly 200 people in the southwestern city of Quetta, which is home to many Hazaras. They are an ethnic group, mostly made up of Shiite Muslims, who migrated from Afghanistan more than century ago.
Those attacks were claimed by Lashkar-e-Jhangvi, a Sunni militant group known for its virulent hatred of Shiite Muslims.
Last year was one of the most deadly for Shiites in the country's history. According to Human Rights Watch, more than 400 Shiite Muslims were killed in targeted attacks across Pakistan in 2012. But with nearly 250 Shiites killed in the three attacks so far, this year is shaping up to be even more dangerous.
Pakistan's intelligence agencies helped nurture Sunni militant groups like Lashkar-e-Jhangvi in the 1980s and 1990s to counter a perceived threat from neighboring Iran, which is mostly Shiite. Pakistan banned Lashkar-e-Jhangvi in 2001, but the group continues to attack Shiites.
Karachi shut down on Monday for a day of mourning to honor the dead. Markets, gas stations and transportation were closed as security officials patrolled the streets.
At the site of the blast, family and friends were looking through the rubble for family members missing after the explosion.
"I am here to look for my relative," said Farzana Azfar. "People say he was here. But people say they have no idea about him. It appears that some bodies are still in the rubble."
With three massive attacks against Shiites in as many months this year, many Pakistanis are questioning why the government does not seem able to protect them.
"Go ask the sleeping government to wake up. Our brothers and sisters are dying every day. But the government is doing nothing. This government is sleeping," said Shagufta Rasheed.
Associated Press writer Muhammed Farooq contributed to this report.