The magnitude 7.3 quake rocked Iran near its Iraq border, killing at least 328 and leaving others trapped beneath the rubble.
Images from inside the country showed the impact of the quake, which struck at 6.18pm GMT yesterday.
The pictures showed streets covered with the wreckage of their buildings, cars crushed in the street, and roads strewn with concrete slabs and smashed glass.
Devastating landslides blocked roads with tumbling debris, cutting off remote villages, and hindering rescue efforts, Iranian Interior Minister Abdolreza Rahmani Fazli said.
Iran’s National Disaster Management Organisation said more than 1,700 people were injured with the total casualty numbers set to soar further.
Many homes in the area, made of weak mud bricks, were brought down by the tremors.
Worst hit was the province of Kermanshah, which saw Sarpol-e Zahab county’s hospital heavily damaged by the disaster.
That devastation meant many of the injured nearby could not be treated.
The province has now announced three days of mourning for its victims.
In Baghdad, tall buildings were also shaken by the huge tremors.
Terrified mother-of-three Majida Ameer said: “I was sitting with my kids having dinner and suddenly the building was just dancing in the air.
”I thought at first that it was a huge bomb.
“But then I heard everyone around me screaming ‘earthquake!'”
Similar scenes unfolded in Erbil, the capital of the Kurdistan Region, and across other cities in northern Iraq, close to the quake’s epicentre.
Towns on both sides of the border were left without electricity as the quake brought down power lines and left valuable infrastructure wrecked.
On the Iraqi side, the most extensive damage was in the town of Darbandikhan, 75 km east of the city of Sulaimaniyah in the semi-autonomous Kurdistan region.
More than 30 people were injured in the town, according to Kurdish Health Minister Rekawt Hama Rasheed.
He warned: ”The situation there is very critical.”
The district’s main hospital was severely damaged and had no power, so the injured were taken to Sulaimaniyah for treatment.
Homes and buildings also had extensive structural damage.
In Halabja, local officials said a 12-year-old boy died of an electric shock from a falling electric cable.
Iraq’s meteorology centre advised people to stay away from buildings and not to use elevators, in case of aftershocks.