Afghan officials say at least 13 people have been killed and some 30 others wounded in an explosion at a mosque in eastern Khost Province that was being used as a voter registration center.
Talib Mangal, a provincial government spokesman, said that an explosive device placed inside the Yaqoubi mosque detonated at around 2.30 p.m. local time on May 6 and caused casualties among civilians who had gathered both for prayers and to register to vote.
Abdul Wali Wahidzai, a provincial council member, said the number of casualties might rise.
No one immediately claimed responsibility, but the extremist group Islamic State (IS) has carried out similar attacks in the past. Taliban militants have also warned people not to take part in the elections.
There have been a number of attacks on voter registration centers since the process began last month.
On April 22, a suicide bombing outside a voter registration center in Kabul killed at least 57 people and wounded 119 others.
IS claimed responsibility for the attack, which occurred in a heavily Shi'a-populated area in the Afghan capital.
Afghan parliamentary elections are scheduled for October 20.
In a separate incident, a vehicle carrying shopkeepers on their way to a market struck a roadside bomb in Afghanistan's northern Faryab Province, killing seven of them.