The leaders of countries around the world have pledged to send support to help rescue efforts in Turkey and Syria.
UK Prime Minister Rishi Sunak said in a statement: "My thoughts are with the people of Türkiye and Syria this morning, particularly with those first responders working so valiantly to save those trapped by the earthquake. The UK stands ready to help in whatever way we can."
Meanwhile, French President Emmanuel Macron described the images coming from both countries as "terrible" and said France "stands ready to provide emergency aid", while German Chancellor Olaf Scholz said his country mourned with the relatives of those killed and "will of course send help".
Israeli PM Benjamin Netanyahu sent his condolences to the citizens of Turkey and said he had instructed "all authorities to prepare immediately to provide medical, rescue and rescue assistance".
The Indian government said that 100 disaster response personnel as well as specially-trained dog squads were ready to be flown to the areas affected, and that medical teams and supplies were also being prepared.
Nato Secretary-General Jens Stoltenberg said he was in touch with Turkey's President Erdogan and was "mobilising support".
People wait in hope for families to be rescued
Meanwhile, rescuers search for survivors under the rubble following an earthquake in Diyarbakir
Rescuers search for survivors under the rubble in Diyarbakir, TurkeyImage caption: Rescuers search for survivors under the rubble in Diyarbakir, Turkey
An old woman is wailing in Kurdish, waiting to hear from her sister-in-law and nieces and nephews who were stuck under the rubble.
Some young neighbours are trying to console her, saying: “They rescued a person a few minutes ago, they will rescue your family, too.”
She is not very hopeful since her family lived in the ground floor of the 12-storey building.
“They were on the ground floor, sleeping, I don’t know if anyone can reach them... and it is very cold, my babies will be frozen under the rubble," she says.
And all of a sudden, the crowd gets loud and clapping is heard. They reach someone under the rubble. It’s not her relatives but still she is glad someone is rescued. But soon enough they are confirmed dead, and a deep silence dominates the crowd.
It’s freezing cold, raining and because of the aftershocks, no one can go closer to their houses. Even though they left their houses in the middle of the night in a hurry... they are too afraid to go back home to pick up some jackets and shoes.
At least seven buildings collapsed in Diyarbakir, 33 people have been confirmed dead and 12 people were rescued from the rubble.
Syria hospital treating quake victims pleads for help
AFP adds from Darkush, Syria: At a hospital in northwest Syria, Osama Abdel Hamid was holding back tears as he recalled on Monday the massive earthquake that toppled his home just hours earlier.
"We were fast asleep when we felt a huge earthquake," Abdel Hamid told AFP at Al-Rahma hospital in Idlib province, where he was being treated for a head injury.
The 7.8-magnitude pre-dawn quake, whose epicentre was near the Turkish city of Gaziantep, wiped out entire sections of cities in Turkey and war-ravaged Syria, killing more than 1,200 people in their sleep.
When it shook the Abdel Hamid family's home in the village of Azmarin, near Syria's border with Turkey, "I woke up my wife and children and we ran towards the exit door," the man said.
"We opened the door, and suddenly the entire building collapsed."
Within moments, Abdel Hamid found himself under the rubble of the four-storey building.
All of his neighbours died, but the family made it out alive.
"The walls collapsed over us, but my son was able to get out," Abdel Hamid said. "He started screaming and people gathered around, knowing there were survivors, and they pulled us out from under the rubble."
They were taken to the hospital in Darkush, a town several kilometres (miles) to the south along the Turkish border.
The facility soon had to take in patients far beyond its capacity and received at least 30 dead bodies.
An AFP photographer saw multiple ambulances arriving at Al-Rahma one after the other, carrying casualties including many children.
"The situation is bad," said Majid Ibrahim, general surgeon at the hospital, where by the late morning some 150 people injured in the quake had arrived.
"A lot of people are still under the debris of the buildings," he told AFP.
"We need urgent help for the area, especially medical help."
- Many 'still trapped' -
At least 592 people were killed across the war-torn country, the Syrian government and rescue workers said.
The official news agency SANA, citing the health ministry, said at least 371 people were killed and 1,089 injured in government-controlled areas.
The White Helmets rescue group said at least 221 were killed and 419 injured in rebel-held areas, and cautioned "the toll may increase as many families are still trapped."
In one crowded hospital room, injured people were lying on beds, some with bandages on their heads and others treated for fractures and bruises.
On one of the beds, a boy whose head was covered in a bandage was sleeping next to another patient.
And in another room, a young girl was crying as she received an injection, her hand in a cast.
Mohammad Barakat, 24, was being treated for a broken leg.
"I took my children and got out of the house," recalled the father of four, lying in bed with wounds covering parts of his face.
"My house is an old one, and construction is very old," he told AFP.
"So I got scared it might collapse on us. The walls of the neighbouring houses began collapsing when we were out in the street."
- Worse than war -
The earthquake hit near Gaziantep in southeastern Turkey at 04:17 am (0117 GMT) at a depth
of about 17.9 kilometres (11 miles), the US Geological Survey said.
Tremors were also felt in Lebanon and Cyprus, AFP correspondents said.
In the town of Sarmada, in the countryside of Idlib province, a block of buildings had been levelled. The remains of solar panels and water tanks as well as mattresses and blankets were scattered above the ruins.
An AFP photographer saw rescue workers start to clear the rubble and remove big pieces of concrete in the hope of finding survivors.
Anas Habbash said he "ran down the stairs like crazy", carrying his son and ushering his pregnant wife outside of the apartment building in the northern city of Aleppo.
"Once we got to the street, we saw dozens of families in shock and fear," the 37-year-old told AFP.
Some knelt down to pray and other started crying "as if it were judgement day".
"I haven't had that feeling all through the years of the war" in Syria since 2011, Habbash said.
"This was much more difficult than shells and bullets."