Suicide bombers attacked a Shi'ite mosque in the southern Afghan city of Kandahar, killing at least 41 people, the second week in a row that militants bombed Friday prayers and killed dozens of worshippers from the minority sect.
There was no immediate claim of responsibility for Friday's attack in Kandahar, but Islamic State claimed the similar bombing a week earlier that killed scores of Shi'ites in the northern city of Kunduz.
Sardar Mohammad Zaidi, imam of the mosque, said there had been four attackers, two of whom blew themselves up at the entrance, allowing the other two to get inside where they detonated their explosives among around 3,000 worshippers just as Friday prayers were ending.
A health official at Kandahar's Mirwais hospital told Reuters it had confirmed 41 dead and was treating 70 wounded.
The attacks have caused shock and terror among members of Afghanistan's Shi'ite minority and undermine the ruling Taliban movement's claim to have restored security since taking control of the country in August.
"When I arrived at the mosque, I saw injured, dead bodies, and people who had fallen on top of each other," said Haji Sarwar Hazara, a local construction contractor who arrived soon after the blast.
"I do not know who did this work, it is the enemy of Islam. But they cannot bring differences among Muslims," he said.
Photographs and mobile phone footage posted by journalists on social media showed many people apparently dead or seriously wounded on the bloody floor of the Imam Bargah mosque, also known as the Fatima mosque, the largest of around 40 Shi'ite mosques in Kandahar.
Taliban spokesman Zabihullah Mujahid said security forces had been ordered to capture the perpetrators and bring them to justice under Islamic law.
Sunni Muslim fighters of Islamic State have repeatedly targeted Shi'ites in the past with large-scale attacks intended to kill civilians, including one that killed scores of schoolgirls in a Shi'ite district of Kabul in May last year.
The Taliban are also strict Sunni Muslims but consider Islamic State their enemy and have pledged to protect all ethnic and sectarian groups since sweeping to power in August as US forces withdrew.
The embassy of Iran, Afghanistan's neighbor and the region's largest Shi'ite power, condemned the attack.
"We hope Taliban leaders take decisive action against these wicked terrorist incidents," it said in a Twitter post.
The UN mission in Afghanistan said those responsible should be held to account.
Taliban special forces arrived to secure the site and an appeal went out to residents to donate blood for the wounded.
The blast, coming so soon after the Kunduz attack, underlined uncertainty over security in Afghanistan as the Taliban grapple with an escalating economic and humanitarian crisis that threatens millions with hunger.
The local affiliate of Islamic State, known as Islamic State Khorasan after an ancient name for the region, has stepped up attacks following the Taliban victory over the Western-backed government in Kabul.
Taliban officials have played down the threat from Islamic State, and dismissed suggestions they may accept US help to fight the group.
But the repeated attacks have caused increasing unease from countries in the region about the potential for militant violence to spill across Afghanistan's borders.
That the Shi'ite minority has again been targeted may also inflame tensions among ethnic and sectarian groups in the country, which is largely Sunni Muslim but ethnically diverse.
Most Shi'ites in Afghanistan belong to the Hazara ethnic group of Persian speakers, who have complained of persecution under the mainly Pashtun-speaking Taliban in the past.