KABUL, Afghanistan — A bomb ripped through a mosque in northern Kabul during Friday prayers, killing 12 worshippers, and wounding 15, Afghan police said.

No one immediately claimed responsibility for the bombing, the latest in a surge in violence as U.S. and NATO troops have begun their final withdrawal from the country, after 20 years of war.

According to Afghan police spokesman, Ferdaws Faramarz, the bomb exploded as prayers had begun. The mosque’s imam, Mofti Noman, was among the dead, the spokesman said and added that the initial police investigation suggests the imam may have been the target.

Taliban spokesman Zabihullah Mujahid denied any insurgent connection to the mosque attack, condemning it and accusing Afghanistan’s intelligence agency of being behind the explosion.

Both the Taliban and government routinely blame each other for attacks. The attackers are rarely identified, and the public is seldom informed of the results of investigations into the many attacks in the capital.

Explosive Hidden in Pulpit at Front of Mosque

One worshipper, Muhibullah Sahebzada, said he had just stepped into the building when the explosion went off. Stunned, he heard the sound of screams, including those of children, as smoke filled the mosque.

Sahebzada said he saw several bodies on the floor, and at least one child was among the wounded. It appeared the explosive device had been hidden inside the pulpit at the front of the mosque, he added.

“I was afraid of a second explosion so I came immediately to my home” he said.

An image circulating on social media shows three bodies lying on the floor of the mosque.

The explosion comes on the second day of a three-day cease-fire announced by the Taliban for the Muslim holiday this week of Eid al-Fitr, which follows the fasting month of Ramadan. The Afghan government has also said it would abide by a truce during the holiday.

So far, many of the attacks in Kabul have been claimed by the Islamic State group’s local affiliate, though the Taliban and government routinely trade blame.

Last week, a powerful car bombing attack in Kabul killed over 90 people, many of them students leaving a girls’ school. The Taliban denied involvement and condemned the attack.

Earlier this week, U.S. troops left southern Kandahar Air Base, where some NATO forces still remain. At the war’s peak, more than 30,000 U.S. troops were stationed in Kandahar, the Taliban heartland. The base in Kandahar was the second largest U.S. base in Afghanistan, after Bagram north of Kabul.