Sources in Nangarhar province confirm that an explosion took place among worshipers in the Spinghar district.
According to locals, the explosion took place around noon on Friday in a mosque.
Details of the cause of the blast and the resulting casualties are not yet available.
Local sources, however, say dozens have been killed and injured.
The Taliban have not yet commented.
This is the third attack on worshipers since the Taliban took control of Afghanistan.
Earlier, the ISKP had targeted worshipers in Kandahar and Kunduz provinces.
No one has yet claimed responsibility for the blast in Nangarhar.