An explosive device was detonated close to the Independent Election Commission's offices in Jalalabad city on Saturday morning, officials confirmed.
Health officials said early reports indicate at least two people were killed and four were wounded.
The provincial governor's spokesman Attaullah Khogyani said one of the wounded was in a critical condition.
The explosion happened at about 11.30am.
Protesters had reportedly been outside the IEC's offices at the time of the explosion.