An explosion at a mosque in the eastern Afghan province of Khost has killed at least 13 people and wounded 31 and the casualty total may rise, a local police official says.
Basir Bina, spokesman for the provincial police, said people were gathered after afternoon prayers in the mosque, which was also being used as a voter registration centre for parliamentary elections due in October.
He said Sunday's blast appeared to have been caused by explosives left in the mosque rather than by a suicide bomber.
There was no immediate claim of responsibility for the explosion, which adds to a series of attacks on preparations for elections seen as a key test of government credibility.
Last month, around 60 people were killed in a suicide attack on a voter centre in the capital Kabul, which was claimed by Islamic State while the Taliban has also warned people not to take part in the elections.