Both Isis and a faction of the Pakistani Taliban have claimed responsibility for a suicide attack on a hospital in Quetta which killed at least 70 people and wounded more than 100.
The bomber struck on Monday as a crowd of mourners, mostly lawyers and journalists, gathered to accompany the body of Bilal Anwar Kasi, a prominent lawyer who was shot and killed earlier on Monday.
At least 70 people were killed and more than 112 wounded, Abdul Rehman Miankhel, a senior official at the government-run Civil Hospital, where the explosion occurred, told reporters.
"There are many wounded, so the death toll could rise," Rehmat Saleh Baloch, the provincial health minister, said.
Isis' Amaq news agency reported the terror group was behind the atrocity. If true, it would mark an alarming development for Pakistan, which has been long plagued by mostly locally-based Islamist militant violence.
"A martyr from the Islamic State detonated his explosive belt at a gathering of justice ministry employees and Pakistani policemen in the city of Quetta," Amaq said in a statement.
Jamaat-ur-Ahrar, a faction of the Pakistani Taliban, earlier said it had carried out the attack.
The movement at one time swore fealty to Isis' Middle East leadership, but later switched back to the Taliban.
"The Tehreek-e-Taliban Pakistan Jamaat-ur-Ahrar (TTP-JA) takes responsibility for this attack, and pledges to continue carrying out such attacks," spokesman Ehsanullah Ehsan said in a statement.
Jamaat-ur-Ahrar was added to the US' list of global terrorists last week, triggering sanctions against the group.
It remains unclear what ties Jamaat-ur-Ahrar retains to Isis, whose leadership is a rival to both the Taliban and al-Qaeda over claims to represent the true Islamic Caliphate.
In September 2014, Jamaat-ur-Ahrar rejected the Pakistani Taliban during a leadership struggle and swore allegiance to Isis.
By March 2015, however, the group was again swearing loyalty to the main Pakistani Taliban umbrella leadership. The reason for its return to the fold remains murky, but Jamaat-ur-Ahrar also never specifically disavowed Isis either.
The motive behind the attack was unclear, but several lawyers have been targeted during a recent spate of killings in Quetta, the provincial capital of Baluchistan, which has a history of militant and separatist violence.
The latest victim, Bilal Anwar Kasi, was shot and killed while on his way to the city's main court complex, senior police official Nadeem Shah told Reuters. He was the president of Baluchistan Bar Association.
The subsequent suicide attack appeared to target his mourners, said Anwar ul Haq Kakar, a spokesman for the Baluchistan government.
"It seems it was a pre-planned attack," he said.
Ali Zafar, president of the Supreme Court Bar Association of Pakistan, told reporters in the eastern city of Lahore: "We [lawyers] have been targeted because we always raise our voice for people's rights and for democracy ... Lawyers will not just protest this attack but also prepare a long-term plan of action."
Monday's attack was the deadliest in Pakistan since an Easter Day bombing ripped through a Lahore park, killing at least 72 people. Jamaat-ur-Ahrar also claimed responsibility for the bombing.
Additional reporting by Reuters
