Iranian officials said 413 people had died in the country, following the quake, the deadliest in the world this year, on Sunday night. It struck about 30 km south of the Iraqi town Darbandikhan, near the north-eastern border with Iran.
Across the border in Iraq, officials said nine people were killed. Tremors were felt as far away as Turkey, Israel, Kuwait and Pakistan.
Authorities said that more than 30,000 houses had been damaged and at least two villages completely destroyed.
Survivors spent Monday night in makeshift camps or in the open. Many whose homes were still intact were frightened of returning because of dozens of aftershocks.
“It is a very cold night… We need help. We need everything. The authorities should speed up their help,” the BBC quoted a homeless young woman in Sarpol-e-Zahab, the town with the maximum number of victims.
Maj Gen Mohammad Ali Jafari, head of the elite Islamic Revolutionary Guards Corps (IRGC), said that the immediate needs were tents, water and food.
The Iranian Red Crescent said many areas lacked water and electricity and that aid supplies were being hampered by blocked roads. Iranian Army helicopters were taking part in the relief effort.
About 30 Red Crescent teams were working in the earthquake zone.
Iran has declared Tuesday a national day of mourning.