Rescuers have dug with their bare hands through the debris of buildings brought down by a powerful earthquake that has killed more than 400 people in the once-contested mountainous border region between Iraq and Iran.
- Authorities say relief effort has been slow
- Worst damage in Kurdish town of Sarpol-e-Zahab
- Iranian Red Crescent says 70,000 people need emergency shelter
Rescue workers and special teams using sniffer dogs and heat sensors searched wreckage, while residents dug frantically through rubble amid sounds of crying.
Blocked roads were making it harder to reach some remote villages, while landslides were also hindering efforts.
Iranian authorities acknowledged the relief effort was still slow and patchy.
More than 70,000 people needed emergency shelter, the head of Iranian Red Crescent said.
Iran's police, Revolutionary Guards and Basij militia forces were sent to quake-hit areas overnight, state TV reported.
Sunday night's magnitude 7.3 earthquake struck about 31 kilometres outside the eastern Iraqi city of Halabja, according to the most recent measurements from the US Geological Survey.
It hit at 9:48pm (local time), just as people were going to bed.
The worst damage appeared to be in the Kurdish town of Sarpol-e-Zahab in the western Iranian province of Kermanshah, which sits in the Zagros Mountains that divide Iran and Iraq.
The quake killed 407 people in Iran and injured 7,156 others, Iran's crisis management headquarters spokesman Behnam Saeedi told state TV.
He said most were treated for minor injuries and released, with fewer than 1,000 still hospitalised.
Questions over disparity in tolls between Iran, Iraq
In Iraq, the earthquake killed at least seven people and injured 535 others, all in the country's northern, semiautonomous Kurdish region, according to its Interior Ministry.
The disparity in the fatality figures immediately drew questions from Iranians, especially because so much of the town was new.
Iraqi seismologist Abdul-Karim Abdullah Taqi, who runs the earthquake monitoring group at the state-run Meteorological Department, said the main reason for the lower casualty figure in Iraq was the angle and direction of the fault line in this particular quake.
Tempers frayed in the quake-hit area as the search went on for survivors amidst the twisted rubble of collapsed buildings.
"We need a shelter," a middle-aged man in Sarpol-e Zahab told state TV.
"Where is the aid? Where is the help?"
Iran's Supreme Leader Ayatollah Ali Khamenei immediately dispatched all government and military forces to aid those affected.
The newly homeless slept outside in cold, huddled around makeshift fires for warmth, wrapped in blankets — as were the dead.
Kokab Fard, a 49-year-old housewife in Sarpol-e-Zahab, said she could only flee empty-handed when her apartment complex collapsed.
"Immediately after I managed to get out, the building collapsed," Ms Fard said.
Reza Mohammadi, 51, said he and his family ran into an alley following the first shock.
"I tried to get back to pick some stuff, but it totally collapsed in the second wave," Mr Mohammadi said.
Ayatollah Khamenei offered his condolences as President Hassan Rouhani's office said Iran's elected leader would tour the damaged areas on Tuesday.
Authorities also set up relief camps and hundreds lined up to donate blood in Tehran, though some on state television complained about the slowness of aid coming.
The quake caused Dubai's skyscrapers to sway and could be felt more than 1,000 kilometres away on the Mediterranean coast. Nearly 120 aftershocks followed.