The jihadist Islamic State claimed it carried out this week's attack on a mosque on the outskirts of the Afghan capital that left 12 worshippers dead, SITE Intelligence Group reported.
The explosion happened inside a mosque in Shakar Darah district of Kabul province during Friday prayers and shattered the relative calm of a three-day ceasefire agreed between the Taliban and the Afghan government.
IS said its fighters had placed an explosive device inside the mosque and detonated it after worshippers arrived to offer prayers on the second day of the Eid al-Fitr holidays, the US monitor of jihadist groups said late Saturday.
Meanwhile, fighting between the Taliban and Afghan government forces resumed in full force yesterday in the restive southern province of Helmand, officials said.
Violence has soared as the United States military presses ahead with a plan to withdraw all of its troops by September, bringing an end to a 20-year military operation in Afghanistan.
"The fighting started early today and is still ongoing," Attaullah Afghan, head of the Helmand provincial council, told AFP. He said Taliban fighters attacked security checkpoints on the outskirts of Lashkar Gah, the capital of Helmand province, and some other districts.
An Afghan army spokesman in the south confirmed fighting had resumed, and the Helmand governor's office said that 21 Taliban fighters had been killed so far.
Washington has vowed to end America's longest war but missed a May 1 deadline to pull out, as agreed with the Taliban last year in return for security guarantees and a promise to launch talks with the Afghan government.