Islamic State claims its fighters are responsible for an attack on a police training college in the southwestern Pakistani city of Quetta, which killed 59 people and wounded more than 100.
Pakistani authorities have blamed another militant group, Lashkar-e-Janghvi, for the late-night siege, though the Islamic State claim included photographs of three alleged attackers.
Hundreds of trainees were stationed at the facility when masked gunmen stormed the college on the outskirts of Quetta late on Monday.
Islamic State's Amaq news agency published the claim of responsibility, saying three IS fighters "used machine guns and grenades, then blew up their explosive vests in the crowd".
Mir Sarfaraz Bugti, home minister of the province of Baluchistan, whose capital is Quetta, said the gunmen attacked a dormitory in the training facility, while cadets rested and slept.
"Two attackers blew up themselves, while a third one was shot in the head by security men," Mr Bugti said.
Earlier, officials had said there were five to six gunmen.
A Reuters photographer at the scene said authorities carried out the body of a teenaged boy who they said was one of the attackers and had been shot dead by security forces.
Prime Minister Nawaz Sharif and Army chief General Raheel Sharif both travelled to Quetta after the attack and participated in a special security meeting on Tuesday afternoon, the prime minister's office said.
One of the top military commanders in Baluchistan, General Sher Afgun, told media that calls intercepted between the attackers and their handlers suggested they were from the sectarian Sunni militant group, Lashkar-e-Jhangvi (LeJ).
Mr LeJ, whose roots are in the heartland Punjab province, has a history of carrying out sectarian attacks in Baluchistan, particularly against the minority Hazara Shias. Pakistan has previously accused LeJ of colluding with al-Qaeda.
Pakistan has improved its security situation in recent years but Islamist groups continue to pose a threat and stage major attacks in the mainly Muslim nation of 190 million.
Islamic State has sought to make inroads over the past year, hoping to exploit the country's growing sectarian divisions.