A bomb exploded at a vegetable market on the outskirts of the Pakistani capital on Wednesday, killing 20 people and injuring about 70, police and hospital officials said.
The deadliest attack in Islamabad in several years followed weeks of preliminary talks with the main Islamist militant
grouping battling the state, the Pakistani Taliban, who last week extended a ceasefire until April 10.
The Pakistani Taliban denied responsibility for the early morning bomb that went off as traders assembled for fruit auctions.
Severed body parts and bloodstained clothes were scattered throughout stalls at the market between Islamabad and its twin city of Rawalpindi. Police said the bomb had been 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 damaged fruit in the mud. Police waved metal detectors over boxes while dazed vendors sat in the wreckage.
Javed Akram Qazi, vice chancellor of the Pakistan Institute of Medical Sciences, said 18 bodies had been brought in to his hospital. Earlier, he had said 23 people were killed but later said authorities had been confused in their reporting.
Another hospital had received two bodies, and about 70 people were injured, said Minister of Health Saira Afzal Tarar.
Rawalpindi is home to the headquarters of the military but the blast occurred far from any army buildings.
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 a 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.
In talks with representatives of the government, the Taliban have demanded the release of hundreds of prisoners and the withdrawal of the army from some semi-autonomous ethnic Pashtun regions where militants shelter along the border with Afghanistan.
The Taliban are fighting to overthrow Pakistan's democratically elected government and impose a strict form of Islamic law.
Pakistan is home to dozens of militant groups. Many are officially banned but nevertheless tolerated by the government in a country that has for decades seem Islamist groups as "assets" for use in the event of war with old rival India, and to pursue objectives in Afghanistan.
Some Islamists, such as the Pakistani Taliban, turned on the state after Pakistan was pressured into siding with the United States in its "war on terror" following the September 11, 2001, attacks on U.S. cities.
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