A powerful earthquake has struck close to Iran's only nuclear power station, killing 37 people and injuring 850, as it destroyed homes and devastated two small villages.

The 6.3 magnitude quake totally destroyed one village, a Red Crescent official told the Iranian Students' News Agency (ISNA).

However, the nearby Bushehr nuclear plant was undamaged, according to Iranian officials and the Russian company that built it.

Across the Gulf, offices in Qatar and Bahrain were evacuated after the quake, whose epicentre was 89km southeast of the port of Bushehr, according to the US Geological Survey.

The early afternoon shock was also felt in Dubai.

The Russian company that built the nuclear power station, 18km south of Bushehr, said the plant was unaffected.

"Personnel continue to work in the normal regime and radiation levels are fully within the norm," Russian state news agency RIA quoted an official at Atomstroyexport as saying.

Iran informed the UN's International Atomic Energy Agency that there was "no damage to the Bushehr Nuclear Power Plant and no radioactive release from the installation".

A Red Crescent official told ISNA that 20 people had been saved by rescue teams searching through the rubble.

Reports in Iranian media said landslides destroyed buildings and crowds gathered in the town of Dashti from outlying areas in search of help.

Military officials said army and police units have been deployed to maintain order.

Water and electricity lines have severed and residents are staying in the streets because of the threat from aftershocks.

Ayatollah Ali Khamenei has offered his condolences to the victims and urged authorities to extend all efforts to save lives and help the victims.