Pakistani men carry an injured blast victim after a bomb explosion at a market in Parachinar, the capital of Kurram tribal district, Pakistan, on Sunday.

A bomb blast ripped through a crowded bazaar in a mainly Shiite area of Pakistan’s northwestern tribal region on Sunday, killing at least 12 people and wounding dozens more, officials said.

The death toll was expected to rise after the explosion at the Eidgah used-clothes market in Parachinar city, the capital of Kurram tribal district on the border with Afghanistan.

“At least 12 have died and around 50 have been injured,” said Amjad Ali Khan, the political administrator of Kurram.

Two senior police officials who requested anonymity confirmed the incident.

“A bomb disposal squad has reached the spot and is trying to ascertain the nature of the the blast,” one of them added.

Local television footage showed hundreds of male marketgoers fleeing the area, which was strewn with clothing and debris, as police tried to cordon off the location and ambulances rushed to the site.

A doctor at the district headquarters hospital, where the wounded were taken, said most of them were in critical condition and the death toll could increase.

No one immediately claimed responsibility for the attack, but the region is known for sectarian clashes between Sunnis and Shiites, who make up roughly 20 percent of Pakistan’s population of 200 million.

Kurram is one of Pakistan’s seven semi-autonomous tribal districts which are governed according to local laws and customs.

They are the frontline of Pakistan’s battle against an insurgency that began in 2004 after the US-led invasion of Afghanistan forced Taliban and Al-Qaeda militants to flee across the border.

The insurgency has claimed the lives of around 25,000 civilians and security forces’ personnel, according to the South Asia Terror Portal.

Overall levels of violence have decreased this year following a nationwide military-led offensive against militants, including a crackdown on groups who target Shiites and preachers who incite hatred.

In July the leader of an anti-Shiite group behind some of Pakistan’s worst sectarian atrocities was killed in a shootout with police, along with 13 other extremists.

The killing of Malik Ishaq, the head of Lashkar-e-Jhangvi who had openly boasted of murdering more than 100 people, was seen by analysts as an extra-judicial killing by the state.

Haroon Bhatti, a key deputy to Ishaq, was killed in a similar shootout late last month. But attacks against the minority persist.

In October a suicide bomber blew himself up at a Shiite religious procession in the southern city of Jacobabad, killing 24.

In May gunmen who pledged allegiance to Daesh opened fire on a bus in Karachi carrying Ismaili Shiites, killing 44.

The deadliest-ever attack against Pakistani Shiites came in January 2013 when a suicide bomber blew himself at a snooker hall in the southwestern city of Quetta.

As rescue workers rushed to the scene, a truck packed with explosives parked nearby also detonated, with the overall toll close to 100 dead.

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