A suicide bomber detonated explosives inside the house of an influential family in eastern Afghanistan, killing at least 13 people, officials said.
Fourteen others were wounded in Sunday's attack in the city of Jalalabad, a hospital official told Al Jazeera.
Attaullah Khogyani, spokesman for the Nangarhar provincial government, said the attacker detonated his explosives at about 10:30am local time (06:00 GMT) at the residential compound of Obaidullah Shinwari.
Among the wounded was Shinwari's father, Malik Osman Shinwari, a prominent tribal elder and a fierce critic of the Islamic State of Iraq and the Levant (ISIL) group, said Khogyani.
The family was celebrating a son's release from Taliban captivity when the suicide bomber struck.
The attack came just days after a deadly assault on the Pakistani consulate in Jalalabad, close to Shinwari's compound, which was claimed by ISIL.
Al Jazeera's Omar al-Saleh said the wounded tribal elder was flown by helicopter to Kabul for medical treatment. His condition was unclear.
"We believe the suicide bomber was disguised as a guest," he reported from the capital Kabul. "The situation in Jalalabad is very volatile. You have both the Taliban and ISIL present there. The two groups are not only fighting the government, but also each other."
Taliban spokesman Zabiullah Mujahid said the group was not responsible for Sunday's attack.
Meanwhile, the Italian foreign ministry said that a "random" rocket landed near the Italian embassy in the Afghan capital Kabul on Sunday evening.
Two guards were reportedly injured when the rocket exploded, but the foreign ministry said it did not believe it had been deliberately targeted.
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Source: Al Jazeera and agencies