At least 17 killed, several injured in blast inside a mosque in Afghanistan

At least 17 people were killed and dozens injured in a blast inside an Afghan mosque during Friday prayers, officials said.

The explosion took place in Haska Mina district of eastern Nangarhar province, and wounded at least 40 people, provincial police spokesman Mubarez Attal told news agencies.

The dead were "all worshippers", he said.

Other officials gave higher tolls, with provincial governor spokesman Attaullah Khogyani saying at least 20 had been killed.

The death may increase, since the roof of the mosque collapsed, as a result of the powerful explosion.

There was no immediate claim of responsibility. Both the Taliban and the Islamic State group are active in Nangarhar province.

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

Civilians have long borne the brunt of violence in Afghanistan's conflict, and the UN called the casualties "totally unacceptable".

The UN laid the blame mainly at the feet of anti-government elements such as IS and the Taliban, though it also documented an alarming rise in casualties caused by pro-government forces.