Overcrowded hospitals in northwest Iran struggled to cope with thousands of earthquake victims on Sunday as rescuers raced to reach remote villages after two powerful quakes killed more than 300 people.

Thousands huddled in makeshift camps or slept in the street after Saturday's quakes for fear of more aftershocks, 60 of which had already struck. A lack of tents and other supplies left them exposed to the night chill, one witness told Reuters.

The US Geological Survey measured Saturday's first quake at 6.4 magnitude and said it struck 60 km (37 miles) northeast of the city 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, 49 km (30 miles) northeast of Tabriz.

More than 1,000 villages in the area were affected by the earthquakes, Ahmad Reza Shaji'i, a Red Crescent official, told the Iranian Students' News Agency (ISNA). Some 130 villages suffered more than 70 percent damage, and 20 villages were completely destroyed, he said.

More than 300 people are now believed to be dead and a further 3,000 people injured, according to ISNA.

Nearly 100 ambulances and 1,100 Red Crescent workers were deployed, Shaji'i said, along with 44,000 food packages and 5,600 tents for shelter. The relief agency had enough supplies and most residents in the area had access to clean water but Shaji'i asked residents to donate cash to the relief effort.

Tehran officials sent condolences to the victims and declared two days of mourning in the province, ISNA reported.

About 36,000 people in the quake-hit area have been given emergency shelter, Masoumi was quoted as saying by ISNA.

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