At least 52 people were killed and more than 100 injured when a powerful explosion ripped through a Sufi shrine in Pakistan's southwestern Baluchistan province on Saturday evening, officials said.
The attack happened as worshipers were in the throes of a ritual dance inside the packed shrine of Shah Bilal Norani in the province's Khuzdar district, Hashim Ghalzai, a local government official, told reporters.
Pakistani officials did not immediately confirm the nature of the blast nor say who they thought was responsible.
Sarfraz Bugti, Baluchistan's home minister, put the toll late Saturday at 52 killed and 105 injured. But many of the wounded were reported to be in critical condition, and the number of deaths was expected to rise.
Lt. Gen. Asim Bajwa, spokesman for Pakistan's army, said the absence of a landing strip in the mountainous terrain was complicating the rescue efforts.
The most seriously injured were being driven to hospitals in the city of Karachi, more than 85 miles away. But Bajwa said a helicopter evacuation would be attempted.
Baluchistan, which has been dealing with a long, low-intensity insurgency by an array of nationalist groups, has suffered a series of deadly attacks in recent months.
Islamic State claimed responsibility for an assault in October in which militants wearing suicide vests stormed a police academy in the provincial capital, Quetta, killing 61 people.
Pakistani military officials blamed that attack on Lashkar-e-Jhangvi al-Alami, a Sunni Muslim extremist group that has links to Islamic State's South Asia wing, Islamic State in Khorasan.
In August, the Taliban breakaway faction Jamaat-ul-Ahrar said its fighters shot and killed the president of the Baluchistan Bar Assn., then sent a suicide bomber to target mourners who had gathered at a hospital in Quetta. At least 70 people were killed.