A powerful explosion tore through a crowded mosque in the Afghan capital, Kabul, during Friday prayers, reportedly killing and injuring dozens of worshipers.
Officials of the ruling Taliban government confirmed the death toll was at least 10, but Sayed Fazil Agha, the prayer leader at the Khalifa Sahib Mosque in the west of the city, said more than 50 worshipers had been killed.
The blast reportedly damaged the roof of the mosque, which caved in on worshipers.
Agha said someone believed to be a suicide bomber joined the gathering and detonated explosives. "Black smoke rose and spread everywhere. Dead bodies were everywhere," he said, adding that his nephews were among the dead.
Taliban spokesman Zabihullah Mujahid condemned the attack. "The perpetrators of these crimes will soon be found and punished, God willing," he tweeted.
No one immediately took responsibility for the deadly assault.
An Italian charity, Emergency, said its Kabul hospital had received 21 wounded people and two bodies. Dozens of victims were being treated in other Kabul medical facilities. Hospitals have received 66 dead bodies and 78 wounded people so far, a health source said.
The blast follows a spate of bombings of Afghan mosques and schools during the Muslim holy month of Ramadan, during which scores of civilians have been killed or injured. The victims were mostly minority Shiite Muslims, including those from the native Hazara ethnic group. Some of the bloodshed has been claimed by Islamic State Khorasan Province, the Islamic State's regional affiliate.
Friday's mosque bombing drew international outrage and calls for punishing those behind it.
"I condemn the senseless and terrible attacks against innocent Afghans this past week, including at Khalifa Sahib Mosque," said Thomas West, the United States special envoy for Afghanistan.
"These attacks must end. Perpetrators must be brought to justice," West tweeted.
The United Nations reiterated that directing attacks against civilians and civilian infrastructure, including mosques, is strictly prohibited under international humanitarian law.
"Today's blast … is yet another painful blow to the people of Afghanistan, who continue to be exposed to unremitting insecurity and violence," said Ramiz Alakbarov, the U.N. humanitarian coordinator for Afghanistan.
"It is unconscionable for civilians to be targeted indiscriminately as they go about their daily business gathering for prayers, going to school or the market, or on their way to work," Alakbarov said.
On Thursday, explosions ripped through two passenger vehicles in the northern Afghan city of Mazar-e-Sharif, killing at least nine people. IS-Khorasan took credit for plotting the bombs that killed Hazara Afghans. Last week, a bomb exploded in a Sunni mosque during Friday prayers in the city of Kunduz, killing 33 worshipers.
The Taliban say they have brought security to the war-torn country since taking power eight months ago and have largely eliminated the IS-Khorasan threat. But the string of deadly terrorist attacks by Islamic State and other groups in recent weeks raises questions about the Taliban claims and their grip on power in Afghanistan.
Some information for this story came from Reuters.