The quake, felt as far west as the Mediterranean coast, triggered landslides, making it hard for rescuers to reach some areas.
At least 335 people have been killed and thousands injured after a magnitude 7.3 earthquake struck near the border between Iran and Iraq.
The earthquake was centred about 19 miles outside the eastern Iraqi city of Halabja at about 6.20pm UK time on Sunday.
It was 15 miles deep – a shallow depth that can cause broader damage – and was felt for about 20 seconds in Baghdad, as well as in Turkey, Kuwait and Israel.
The tremor killed 328 people in Iran, where state news agencies reported 3,950 injured.
At least seven deaths were reported in neighbouring Iraq, with 535 people hurt.
The quake triggered landslides in the mountainous region along the Iran-Iraq border, also destroying buildings, shattering windows and sending people running for safety.
TV reports indicate that more than half the Iranian casualties are from the town of Sarpol-e-Zahab, and the district of Ezgeleh, which have a combined population of 30,000.
The area, about 10 miles from the border with Iraq, is in the Kermanshah province.
Its governor told state TV: “There are still people under the rubble.
“We hope the number of dead and injured won’t rise too much, but it will rise.”
Residents of Sarpol-e-Zahab described fleeing empty-handed as their homes collapsed, and said the power and water supply in the town was out. More than 100 aftershocks followed the quake.
At least three emergency relief camps have been set up after the only hospital in the town was badly damaged.
Head of emergency medical services Pirhossein Koulivand said it was “difficult to send rescue teams to the villages because the roads have been cut off – there have been landslides”.
Nevertheless, dozens of rescue teams are searching for survivors in larger towns and Red Cross teams are on their way.
In Iraq, the most extensive damage was seen in the town of Darbandikhan, which is in the Kurdish region, where more than 30 people were injured.
Local health minister Rekawt Rasheed said the situation was “critical”, made worse by the fact that the district’s main hospital was badly damaged and without power.
The Turkish Red Crescent has sent assistance including 33 aid trucks, 3,000 tents and heaters, 10,000 beds and blankets and food to Sulaymaniyah, and the military has dispatched a cargo plane of aid.
Relations between Turkey and the Kurdish region of northern Iraq have been tense since the Kurds held an independence referendum in September.
Iran’s Supreme Leader, Ayatollah Ali Khamenei, offered his condolences and urged rescuers and government agencies to do all they can to help those affected by the quake.
The region has regular earthquakes and last night’s struck along a 930-mile fault line between the Arabian and Eurasian tectonic plates, which runs through western Iran and into Iraq’s northeast.
One of the region’s worst quakes struck Bam in Iran in 2003 and killed at least 31,000 people.
There have been two major quakes since then – in 2005 more than 600 people were killed and in 2012 about 300 died.