A car bomb killed at least 26 people at a gathering of Taliban and Afghan armed forces in the eastern city of Nangarhar on Saturday, an official said, as soldiers and militants celebrated an unprecedented Eid ceasefire, Reuters reported.

Islamic State claimed responsibility. The group’s Amaq news agency said the target was “a gathering of Afghan forces” but gave no details. The Taliban had already denied involvement.

Dozens of unarmed Taliban militants had earlier entered the Afghan capital and other cities to celebrate the end of the Ramadan fasting season. Soldiers and militants exchanged hugs and took selfies on their smartphones.

Attaullah Khogyani, spokesman for the provincial governor of Nangarhar, confirmed a car bomb was responsible for the blast in the town of Ghazi Aminullah Khan, on the main Torkham-Jalalabad road, and said that dozens were wounded. He had earlier said a rocket-propelled grenade was to blame.

The Taliban announced a surprise three-day ceasefire over the Eid holiday, which began on Friday, except against foreign forces. It overlaps with an Afghan government ceasefire which lasts until Wednesday.

President Ashraf Ghani said in an address to the nation that he would extend the ceasefire with the Taliban but did not give a time-frame. He also asked the Taliban to extend their three-day ceasefire, which is due to end on Sunday, and begin peace talks.

It was not clear if Ghani knew about the bomb in the east when he made his address.

U.S. Secretary of State Mike Pompeo echoed Ghani’s address, saying peace talks would have to include a discussion on the role of “international actors and forces”.

“The United States is prepared to support, facilitate, and participate in these discussions,” Pompeo said in a statement. “... The United States stands ready to work with the Afghan government, the Taliban, and all the people of Afghanistan to reach a peace agreement and political settlement that brings a permanent end to this war.”