Iranian rescue teams are searching through the rubble of collapsed buildings for survivors from two strong earthquakes which left at least 250 people dead.
The 6.4 and 6.3 quakes struck near Tabriz and Ahar on Saturday afternoon, and more than 2,000 are believed injured, many in outlying villages.
Thousands spent the night in emergency shelters or in the open and there have been more than 55 aftershocks.
Relief agencies are providing survivors with tents, bread and drinking water.
Hundreds of people were rescued overnight but that the continuing aftershocks have made the operation exhausting work.
The numbers of victims is expected to rise.
All the deaths reported so far have been in rural areas, said local officials, an indication of the poorer quality of housing outside urban areas.
Reports say phone lines to many villages have been cut off, confining rescuers to radio contact.
“The quake has created huge panic among the people,” said one resident of Tabriz.
“Everyone has rushed to the streets and the sirens of ambulances are everywhere.”
The towns of Haris and Varzaqan in East Azerbaijan province in north-western Iran were among those that suffered casualties, local crisis committee chief Khalil Saei told state TV according to the Associated Press.
“The magnitude of the disaster is so huge that officials are just managing to get enough people in from other provinces to help out,” one Iranian Red Crescent worker told the AFP news agency.
Iran’s Deputy Interior Minister Hassan Ghadami told the official Fars news agency that about 110 villages had been damaged.
State TV said at least six villages were totally flattened, with 60 other villages sustaining damage ranging from 50% to 80%.
“This village is a mass grave,” said Alireza Haidaree, who had been searching for survivors in his home of Baje Baj.
“There are so many other villages that have been completely destroyed,” he told AFP. Locals said 33 of the villages 414 residents had died.
Sixty-six rescue teams have been sent to the region, along with about 200 ambulances and five helicopters.
“Unfortunately there are still a number of people trapped in the rubble but finding them is very difficult because of the darkness,” news agency Fars quoted national emergency head Gholam Reza Masoumi as saying.
State TV broadcast footage of dozens of families sleeping outdoors in parks, and bodies lying on the floor of a morgue in Ahar, including those of children.
As morning came, search teams with sniffer dogs began working through the wreckage in Tabriz.
The timing of the quake, towards the end of the day in the holy month of Ramadan, meant it caught many people indoors as they preparing to break their day of fasting.
A Red Crescent official estimated that 16,000 people had been given emergency shelter in a sports stadium after they were forced to leave their homes.
The organization has provided 3,000 tents, blankets, tons of food and blood supplies.
The Turkish Red Crescent said it was sending a truck full of emergency supplies to the border.
President Mahmoud Ahmadinejad’s office posted a statement on its website expressing condolences to those in the disaster zone and calling on authorities to “mobilize all efforts to help the affected populations,” AFP reports.
A provincial official warned people to stay outdoors overnight because of the risk of aftershocks.
“My family is really terrified. It is night time now but we cannot sleep,” said Tabriz resident Amina Zia.
“This earthquake was… very strong and violent.”
The first quake struck 23 km (14 miles) south-west of Ahar and 58 km (36 miles) north-east of Tabriz at 16:54 local time on Saturday, said the US Geological Survey.
The second earthquake struck just 11 minutes after the first, slightly closer to Tabriz.
Iran straddles a major geological fault line, making it prone to seismic activity. In 2003 an earthquake in the city of Bam left more than 25,000 people dead.
Iran’s earthquake history:
• March 2006 – at least 70 people are killed and nearly 1,000 injured by a 6.0 magnitude quake in Lorestan province
• February 2005 – more than 500 people killed by a strong quake near Zahran, in Kerman province
• December 2003 – a 6.6 magnitude quake destroys the ancient city of Bam, killing more than 25,000 people
• May 1997 – more than 1,600 killed in Birjand, eastern Iran, in a 7.1 magnitude quake
• February 1997 – a 5.5 magnitude quake kills about 1,000 in north-western Iran
• June 1990 – some 40,000 die in a tremor in the northern Gilan province