KABUL, Afghanistan -- At least five civilians were killed Sunday in a bomb blast outside a Kabul mosque, a Taliban official said. It was the deadliest attack in the Afghan capital since U.S. forces left at the end of August.
There was no immediate claim of responsibility, but suspicion fell on Islamic State extremists who have stepped up attacks on the Taliban in recent weeks, particularly in an IS stronghold in eastern Afghanistan.
An apparent roadside bomb went off at the gate of the sprawling Eid Gah Mosque in Kabul at a time when a memorial service was being held for the mother of chief Taliban spokesman Zabihullah Mujahid. Five people were killed, said Qari Saeed Khosti, the spokesman of the Interior Ministry.
The explosion underscored the growing challenges the Taliban face just weeks after they took control of Afghanistan in a blitz campaign, culminating in their takeover of Kabul on Aug. 15.
During their 20-year insurgency, the Taliban themselves had frequently carried out bombing and shooting attacks, but are now faced with trying to contain rival militants using the same methods. The growing security challenges come at a time of an economic meltdown, as the Taliban struggle to run the country without the massive foreign aid given to U.S.-backed government they toppled.
Three suspects were arrested in Sunday's explosion in Kabul, said Bilal Karimi, a Taliban spokesman. He said Taliban fighters were not harmed.
Mohammad Israil, a Kabul resident, said he heard "a loud sound" and saw people running away. An Italian-funded emergency hospital in Kabul tweeted it had received four people wounded in the blast.
The area around the mosque was cordoned off by the Taliban, who maintained a heavy security presence. Later in the afternoon, the site was cleaned. The only signs of the blast was slight damage to the ornamental arch by the entrance gate.
Meanwhile, more than 100 young artists, teachers and their relatives affiliated with the Afghanistan National Institute of Music, a celebrated school that became a target of the Taliban in part for its efforts to promote the education of girls, fled the country Sunday, the school's leaders said.
The musicians, many of whom have been trying to leave for more than a month, boarded a flight from Kabul's main airport and arrived in Doha, the capital of Qatar, around midday Eastern time, according to Ahmad Naser Sarmast, the head of the school, who is currently in Australia. In the coming days, they plan to resettle in Portugal, where the government has agreed to grant them visas.
"It's already a big step and a very, very big achievement on the way of rescuing Afghan musicians from the cruelty of the Taliban," Sarmast, who opened the school in 2010, said in a statement. "You cannot imagine how happy I am."
The musicians join a growing number of Afghans who have fled the country since August, when the Taliban consolidated their control of the country amid the withdrawal of U.S. forces. Among figures in the arts and sports worlds who have escaped are members of a female soccer team who resettled in Portugal and Italy.
Still, hundreds of the school's students, staff and alumni remain in Afghanistan and face an uncertain future amid signs that the Taliban will move to restrict nonreligious music, which they banned outright when they previously led Afghanistan, from 1996 to 2001.
The school's supporters, a global network of artists, philanthropists, politicians and educators, plan to continue to work to get the remaining musicians out of Afghanistan. "The mission is not complete," said Sarmast, an Afghan music scholar. "It just began."
The school has faced threats from the Taliban for years, and in 2014 Sarmast was wounded by a Taliban suicide bomber.
In the final days of the American war in Afghanistan, the school's supporters led a frantic and ultimately unsuccessful attempt to evacuate nearly 300 students, teachers and staff affiliated with the school, along with their relatives. The operation was backed by prominent politicians and security officials in the United States.
At one point, the musicians sat in seven buses near an airport gate for 17 hours, hoping to get on a waiting plane. But the plan fell apart at the last minute when the musicians were not able to obtain entry to the airport and as fears of a possible terrorist attack escalated.
Since the Taliban returned to power, the school has come under renewed scrutiny. Sarmast and the school's supporters have worked for weeks to help get students, alumni, staff and their relatives out of the country, fearing for their safety.
The Taliban have tried to promote an image of tolerance and moderation since returning to power, vowing not to carry out reprisals against their former enemies and saying that women would be allowed to work and study "within the bounds of Islamic law."
But they have sent signals that they will impose some harsh policies, including on culture. A Taliban spokesperson recently said that music would not be allowed in public.
Islamic State militants have stepped up attacks against the Taliban since their mid-August takeover, signaling a widening conflict between them. IS maintains a strong presence in the eastern province of Nangarhar, where it has claimed responsibility for several killings in the provincial capital of Jalalabad.
In late August, an IS suicide bomber targeted American evacuation efforts at Kabul's international airport. The blast killed 169 Afghans and 13 U.S. service members and was one of the deadliest attacks in the country in years.
Attacks in Kabul have so far been rare, but in recent weeks, the Islamic State has shown signs it is expanding its footprint beyond the east and closer toward the capital.
On Friday, Taliban fighters raided an IS hideout just north of Kabul in Parwan province. The raid came after an Islamic State roadside bomb wounded four Taliban fighters in the area.
Information for this article was contributed by Samya Kullab of The Associated Press and by Javier C. Hernandez of The New York Times.