At least 59 police trainees were killed and more than 100 were wounded in an overnight raid by militants on a police academy in southwest Pakistan, officials said.
Health authorities in Balochistan Province said that more than 58 had died and dozens more seriously wounded cadets from the academy outside Quetta had arrived at hospitals.
They said that most of deaths occurred when the militants, who used guns to fight their way into the compound, killing a guard in the process, detonated explosive vests.
The Islamic State (IS) militant group has claimed responsibility for the attack although Pakistani authorities had initially pinned it on a group linked with the Taliban.
According to reports, between three and six armed men attacked the dormitory of the training center on the outskirts of Quetta where cadets were resting and sleeping, provoking a counterterrorism response from the army and Frontier Corps.
Sarfaraz Bugti, Balochistan Province Interior Minister, said more than 200 of the 700 cadets at the academy were immediately rescued "by God's grace."
Security forces killed one of the attackers and two died when they detonated their explosive vests, he said.
Bugti said the hours-long counterterrorism operation mostly ended around 4 a.m. local time, but "cleanup" operations were continuing.
Hours after the attack, IS claimed responsibility for the attack.
An IS news agency said on October 25 that "Islamic State fighters” carried out the assault.
Earlier, however, Major General Sher Afgan, chief of the paramilitary Frontier Corps in Balochistan, which led the counteroperation, said the militants belonged to the Al-Alimi faction of the Lashkar-e-Jhangvi militant group, which is affiliated with the Pakistani Taliban.
"They were in communication with operatives in Afghanistan," he said.
The police academy has come under attack twice in the past, in 2006 and 2008.
With reporting by Dawn, Geo TV, AP, AFP, dpa, Radio Mashaal, and Reuters
