Thousands huddled in makeshift camps or slept in the streets after Saturday's quakes in fear of more aftershocks, 40 of which have struck. A lack of tents and supplies left them exposed to the cold, a witness said.

Casualty figures are expected to rise, officials said, because some of the injured were in critical condition and hundreds were trapped under rubble, inaccessible to rescue workers hampered by darkness.

"I saw people whose entire home was destroyed and all their livestock killed," Tahir Sadati, a photographer, said by telephone. "People need help. They need warm clothes, tents, blankets and bread."

The worst damage and most casualties appeared to have been in rural villages around the towns of Ahar, Varzaghan and Harees, near the major city of Tabriz, Iranian media reported.

Many villages are hard to reach by road.

Hospitals in Tabriz, Ardabil and other cities nearby took in many injured, the Iranian media said. Long queues of survivors waited to be treated.

Aidin, a Tabriz resident, said he went to give blood at a hospital on Saturday and saw staff struggling to cope with the influx of patients. Most had been taken to hospital by their family, he said, indicating a shortage of ambulances.

The US Geological Survey measured the first quake at 6.4 magnitude and said it struck 60km northeast of Tabriz, a trading hub far from Iran's oil-producing areas and known nuclear facilities.

The second, measuring 6.3, struck 11 minutes later near Varzaghan, 49km northeast of Tabriz.

Twelve villages were destroyed and about 60 had more than 50% damage, Iranian media reported.

About 110 villages were damaged, Deputy Interior Minister Hassan Ghadami told the Fars news agency.

Ghadami said 250 people had been killed and Red Crescent spokesman Hossein Derakhshan said more than 2000 were believed to have been injured.

Seventy-one ambulances and 40 units trained to find survivors were deployed to the affected areas with more than 5000 tents, Derakhshan said.

About 16000 people in the quake-hit area have been given emergency shelter, Red Crescent official Mahmoud Mozafar said.

Iranian MP Mohammad Hassan-Nejad warned that if relief efforts did not speed up the death toll would quickly rise.

Iran is situated on major tectonic fault lines and has been hit by several devastating earthquakes in recent years.