A local government spokesperson confirmed the death toll to NBC News. Attaullah Khogyani, spokesman for Nangarhar province's governor, said at least 33 people were wounded in the explosion.
The blast took place as dozens of people gathered inside the mosque for weekly Friday prayers.
There was no immediate claim of responsibility.
Both the Taliban and the Daesh (ISIL or ISIS) group are active in eastern Afghanistan, especially Nangarhar province.
On Thursday, a UN report said more than 2,500 civilians were killed and over 5,600 wounded in the first nine months of this year.