A bomb exploded in a crowded market on the outskirts of Islamabad on Wednesday (local time), killing 20 people and wounding about 70 in the deadliest attack in the Pakistani capital in years.
The attack was claimed by man saying he represented a Baluch separatist group, although Reuters had no way to verify the call, which came from an anonymous telephone number.
If true, it would be the first attack in the capital carried out by Baluch separatist rebels and a significant escalation of Pakistan's western insurgency, which has often been overshadowed by the fight against the Taliban to the north.
The Baluch rebels usually confine attacks to their own province, although they have bombed gas pipelines in Punjab in recent months.
"We conducted (the bombing) in retaliation for the military operation," said Mureed Baloch, referring to an operation on Monday in which the Pakistani military claimed to have killed 30 Baluch insurgents.
Baloch said he was from the United Baloch Army, which is banned by the Pakistani government for its militant activities.
Wednesday's early morning bomb targeted a throng of traders assembled for fruit auctions.
Severed body parts and bloodstained clothes were scattered throughout the market, located between Islamabad and its twin city of Rawalpindi. Police said the bomb was hidden in a box of guava fruit.
"Body parts went everywhere and even hit other people on the head," said Shaheen, a market worker who only gave one name.
Bloody sandals lay amid boxes of straw and fruit squashed in the mud. Police waved metal detectors over boxes while dazed vendors sat in the wreckage. Many of those who worked in the market were poor families living in a nearby slum who had fled fighting in northern Pakistan.
Javed Akram Qazi, vice chancellor of the Pakistan Institute of Medical Sciences, said 18 bodies had been brought in to his hospital.
Another hospital had received two bodies, and about 70 people were wounded, said Minister of Health Saira Afzal Tarar.
The Pakistan Taliban condemned the attack and blamed it on "hidden hands".
"The deaths of innocent people in attacks on public places are saddening," the group's spokesman, Shahidullah Shahid, said in an unusually strongly-worded statement.
"Such attacks are wrong and against Islamic law."
The Taliban regularly bomb schools, marketplaces and public transport. Authorities say they have killed tens of thousands of Pakistanis.
The Taliban are separate to the Baluch insurgents, who want independence for Pakistan's biggest and poorest province. Baluchistan, in the west of the country, makes up nearly half of Pakistan's land mass but is arid and poverty stricken.
Separatist rebels accuse the government of exploiting the region's rich natural resources, including gas, copper and gold, but abandoning its people. They also say government-backed death squads frequently abduct, torture and kill civilians, a policy dubbed "kill and dump" by international human rights groups.
But the rebels also frequently target civilians, including teachers and doctors posted to Baluchistan from other parts of the country. The Pakistani government accuses its arch-rival India of fomenting the Baluch insurgency.
On Tuesday (local time), Baluch insurgents claimed responsibility for bombing a train and killing 14 passengers in Baluchistan.