The blast took place in Haska Mina district in Nangarhar province, and wounded at least 40 people.

Villagers searched for the bodies of their loved ones on Saturday in the rubble of a mosque in eastern Afghanistan that collapsed in a blast during Friday prayers, killing 70 people including dozens of children, officials said.

The attack -- the country's second most deadly this year -- took place in Haska Mina district of eastern Nangarhar province and also wounded at least 36 people.

"We have reports that the death toll has reached 70 in yesterday's incident," the provincial governor's spokesman Attaullah Khogyani told AFP.

"We have sent assistance to the district that includes food and other items," he said.

Witnesses said the roof of the mosque fell through after a "loud" explosion, the cause of which was still being investigated Khogyani said.

At least 27 of the victims were school children, said Asif Shinwari, a spokesman for Nangarhar's education department.

"They were ninth- to tenth-graders. Sixteen school children were wounded," he told AFP, adding that children usually studied at the mosque after prayers.

About 350 worshippers were inside the mosque when the blast happened, according to local residents.

"We are still searching for bodies. Most of those who were killed were children or young boys under 18," resident Omar Ghorzang said.

Donya Gul, another local resident who lost a brother and eight cousins in the incident, also said some people were still missing.

"They buried the bodies yesterday and they buried the bodies today... We are searching for at least five more people. We might only find the pieces of their bodies," he said.

No one has claimed responsibility for the blast. A spokesman for the Taliban said the group "condemned this atrocity in the strongest terms" and labelled it a "major crime".

ISIS is also active in Nangarhar.

The attack came after the United Nations released a report on Thursday saying an "unprecedented" number of civilians were killed or wounded in Afghanistan from July to September.

The figures -- 1,174 deaths and 3,139 injured from July 1 until September 30 -- represent a 42 percent increase compared to the same period last year.

The UN laid most of the blame for the spike at the feet of "anti-government elements" such as the Taliban, who have been carrying out an insurgency in Afghanistan for more than 18 years.

The Taliban rejected the report.