Countries around the world dispatched teams to assist in the rescue efforts, and Turkey's disaster management agency said more than 24,400 emergency personnel were now on the ground. But with such a wide swath of territory hit by Monday's earthquake and nearly 6,000 buildings confirmed to have collapsed in Turkey alone, their efforts were spread thin.
Attempts to reach survivors were also impeded by temperatures below freezing and close to 200 aftershocks, which made the search through unstable structures perilous.
Across Hatay province, just southwest of the earthquake's epicenter, officials say as many as 1,500 buildings were destroyed and many people reported relatives being trapped under the rubble with no aid or rescue teams arriving.
Nurgul Atay told The Associated Press she could hear her mother's voice beneath the rubble of a collapsed building in the city of Antakya, the capital of Hatay province, but that her and others efforts to get into the ruins had been futile without any rescue crews and heavy equipment to help.
"If only we could lift the concrete slab we'd be able to reach her,'' she said. "My mother is 70-years-old, she won't be able to withstand this for long.''
In areas where teams worked, occasional cheers broke out through the night as survivors were brought out of the rubble.
A navy ship docked on Tuesday at the province's port of Iskenderun, where a hospital collapsed, to transport survivors in need of medical care to the nearby city of Mersin. Thick, black smoke rose from another area of the port, where firefighters have not yet been able to douse a fire that broke out among shipping containers that were toppled by the earthquake.
In the Turkish city of Gaziantep, a provincial capital about 33 kilometers (20 miles) from the epicenter, people took refuge in shopping malls, stadiums, mosques and community centers.
The quake, which was centered in Turkey's southeastern province of Kahramanmaras, sent residents of Damascus and Beirut rushing into the street and was felt as far away as Cairo.
The medical aid organization Doctors Without Borders confirmed Tuesday that one of its staff members was among the dead after his house in Syria's Idlib province collapsed, and that others had lost family members.
"We are very shocked and saddened by the impact of this disaster on the thousands of people touched by it, including our colleagues and their families,'' said Sebastien Gay, the group's head of mission in Syria.
Gay said health facilities in northern Syria were overwhelmed with medical personnel working around "around the clock to respond to the huge numbers of wounded.''
In Turkey's Hatay province, thousands of people sheltered in sports centers or fair halls, while others spent the night outside, huddled in blankets around fires.
Turkish President Recep Tayyip Erdogan declared seven days of national mourning.
War-ravaged Syria is calling on the United Nations and all member states to help with rescue efforts, health services, shelter and food aid following a massive earthquake that killed thousands in Syria and Turkey.
The quake-damaged area in Syria is divided between government-held territory and the country's last opposition-held enclave, which is surrounded by government forces and borders Turkey.
Syria's U.N. Ambassador Bassam Sabbagh told reporters the U.N. secretary-general "assured us that the U.N. will do all it's possible in helping Syria in this very difficult situation.'' Sabbagh said he had delivered a letter to Guterres from the country's foreign minister requesting help.
At least 3,381 people were killed in 10 Turkish provinces, with more than 20,000 injured, according to the latest figures from Turkish authorities on Tuesday. The death toll in government-held areas of Syria climbed to 769 people, with some 1,450 injured, according to the Health Ministry. In the country's rebel-held northwest, groups that operate there said at least 450 people died, with many hundreds injured.
That brought the overall total to 5,021.
Authorities fear the death toll will keep climbing as the rescuers look for survivors among tangles of metal and concrete spread across the region beset by Syria's 12-year civil war and refugee crisis.
The quake piled more misery on a region that has seen tremendous suffering over the past decade. On the Syrian side, the affected area is divided between government-controlled territory and the country's last opposition-held enclave, which is surrounded by Russian-backed government forces. Turkey is home to millions of refugees from the Syrian civil war.
In the rebel-held enclave, hundreds of families remained trapped in rubble, the opposition emergency organization known as the White Helmets said in a statement. The area is packed with some 4 million people displaced from other parts of the country by the war. Many live in buildings that are were already damaged by military bombardments.
Strained medical centers quickly filled with injured people, rescue workers said. Some facilities had to be emptied, including a maternity hospital, according to the SAMS medical organization.
More than 7,800 people were rescued across 10 provinces, according to Orhan Tatar, an official with Turkey's disaster management authority.
The region sits on top of major fault lines and is frequently shaken by earthquakes. Some 18,000 were killed in similarly powerful earthquakes that hit northwest Turkey in 1999.
In the latest pledges of international help, South Korean President Yoon Suk Yeol said he was preparing to swiftly dispatch a 60-person search and rescue team as well as medical supplies. Pakistan's government sent a flight carrying relief supplies and a 50-member search and rescue team early Tuesday, and said there will be daily aid flights to Syria and Turkey from Wednesday. India said it would send two search and rescue teams, including specially trained dogs and medical personnel. Britain is sending 76 search-and-rescue specialists with equipment and dogs, as well as an emergency medical team, to Turkey.U.S.
Russian President Vladimir Putin told Syrian President Bashar Assad in a phone call that Moscow will deliver urgent aid and send rescue workers to assist the earthquake-hit country. The Russian military in Syria has deployed 10 units numbering 300 people that started clearing the debris and searching for survivors, the Russian Defense Ministry said.President Joe Biden called Erdogan to express condolences and offer assistance to the NATO ally. The White House said it was sending search-and-rescue teams to support Turkey's efforts.
The U.S. Geological Survey measured Monday's quake at 7.8, with a depth of 18 kilometers (11 miles). Hours later, another quake, likely triggered by the first, struck more than 100 kilometers (60 miles) away with 7.5 magnitude.
The second jolt caused a multistory apartment building in the Turkish city of Sanliurfa to topple onto the street in a cloud of dust as bystanders screamed, according to video of the scene.
Thousands of buildings were reported collapsed in a wide area extending from Syria's cities of Aleppo and Hama to Turkey's Diyarbakir, more than 330 kilometers (200 miles) to the northeast.
The earthquake was the biggest recorded worldwide by the U.S. Geological Survey since one in the remote South Atlantic in August 2021.
Another earthquake of 5.6 magnitude struck central Turkey on Tuesday, the European Mediterranean Seismological Centre said.
* This story has been edited by Ahram Online