Latest Update: The casualties reported in the terror attack have risen to almost 60.
Gunmen wearing explosive vests raided a police training college near the southwestern city of Quetta late on Monday, killing at least 44 people and wounding another 118.
The brazen attack on the Balochistan Police College ended after security forces launched a military counter-operation against the militants, who took hostages at the facility where some 700 cadets are based.
"They first targeted the watch tower sentry, and after exchanging fire, killed him and were able to enter the academy grounds," Sarfaraz Bugti, the home minister of Balochistan province, told reporters.
One of the attackers was killed by security forces and two others detonated their suicide vests, he said. Earlier, authorities put the number of militants at between four and six.
Major General Sher Afgan, chief of the paramilitary Frontier Corps in Balochistan, said "the attack was over in around three hours after we arrived."
No one claimed credit for the attack, the third deadiest in Pakistan this year. Authorities blamed the Al-Alimi faction of the Lashkar-e-Jhangvi, a militant group tied to the Pakistani Taliban. Bugti tweeted the militants were in contact with "handlers" in Afghanistan.
Balochistan has been the center of a low-level Baloch separatist insurgency and the target of Islamist militant attacks in the past.
Earlier on Monday, gunmen killed two customs officers and wounded a third near the town of Surab, about 145 kilometers south of Quetta. Also on Monday, gunmen killed an intelligence officer in northwestern Khyber Pakhtunkhwa province. That attack was claimed by the Pakistani Taliban.
On Sunday, gunmen from the Baloch Liberation Army killed two coast guards and a civilian in a coastal town in the same province.
A suicide bombing on a hospital in Quetta in August killed 73 people, many of them lawyers mourning a colleague who had been fatally shot. Both the "Islamic State" and a faction of the Pakistani Taliban claimed the attack.