A bomb exploded in a mosque in southern Iran on Saturday, killing at least eight people and wounding more than 60 others, Iranian media reported.

Ambulances rushed to the scene of the blast in a crowded district in the city of Shiraz, state television said.

"The death toll has reached eight and about 66 injured," the semi-official Fars news agency said, quoting a police official, identified only as General Zamani.

The agency, quoting an unnamed official, said the death toll was expected to rise because some of the wounded were in a critical condition.

State television urged people in Shiraz to donate blood for the injured, adding that all nurses in the city had been called in on duty.

The official IRNA news agency said the bomb exploded during an address by a cleric in the Shohada mosque in Shiraz.

Fars said on Saturday nights the cleric usually gave speeches on the Baha'i faith, an offshoot of Islam considered heretical by Iran's Shi'ite Muslim establishment and its members claim they face discrimination and persecution in Iran.

Iran says all Iranians, regardless of creed, enjoy the same rights. Local officials were not immediately available for comment on the blast.

UNDER INVESTIGATION

No one has claimed responsibility for the blast but the deputy governor of the province, Mohammad Reza Hadaegh, told state television the cause of the blast was under investigation.

Security is normally tight in Iran, where bomb attacks have been rare in recent years. However, in 2005 and 2006, several people were killed in a string of blasts in the southwestern oil city of Ahvaz.

Sixty-five men were arrested in February and accused of being behind a bombing that killed members of the elite Revolutionary Guards in a southeastern border province, which has a minority Arab population.

Tehran has in the past accused Britain and the United States of trying to destabilize the country by supporting ethnic minority rebels operating in sensitive border areas.

Washington accuses Iran of destabilizing Iraq by supporting Iraqi Shi'ite militia groups.

The United States also is leading efforts to isolate Iran over its nuclear programme, which the West fears is a cover to acquire nuclear bombs. Tehran says its atomic work is solely to generate electricity.