An explosion at a prominent Shi'ite Muslim mosque in the southeast Iranian city of Zahedan killed 30 people and wounded 60, the semi-official news agency ILNA reported.

The agency said the blast was a suicide bombing but no person or group had claimed responsibility.

Shortly after the explosion, security forces discovered and defused a second bomb near the mosque, the semi-official FARS news agency reported.

The attack was carried out on a public holiday honoring the first Shi'ite Imam, Ali Ebne-Abitaleb, after whom the mosque is named. Zahedan is a mostly Sunni city.

The provincial governor told state television the explosion occurred at about 7:45 p.m. (1515 GMT) when many people were inside the mosque for prayers.

Zahedan is the capital of Sistan-Baluchestan province which shares a border with Pakistan. The province faces serious security problems and there are frequent clashes between police and drug dealers and bandits.