Speaking in the House of Commons, foreign secretary James Cleverly said the Foreign Office was working to support 35 British nationals impacted by the earthquakes – and confirmed three British nationals were still unaccounted for. Governments in Turkey and Syria have said the death toll is at least 5,000, although it is expected to be higher.
The 7.8-magnitude quake hit Turkish city Gaziantep in the early hours of Monday, reducing thousands of homes and buildings across the south of the country and northern Syria to rubble as people slept. Four Scottish firefighters are among a 77-strong rescue team sent from the UK to provide specialist technical support to the rescue effort.
"We assess that the likelihood of large-scale British casualties remains low," Mr Cleverly said. "As of this morning, we know that three British nationals are missing."
Turkish president Recep Tayyip Erdoğan said the ten provinces affected by the quake would be declared a disaster zone, adding 13 million of the country's 85 million population were affected in some way. He said people who lost their homes in the earthquake would be put up in hotels in the tourist region of Antalya as a temporary measure.
More than 8,000 people have been pulled from the debris in Turkey alone, and some 380,000 have taken refuge in government shelters or hotels.
For the entire quake-hit area, that number could be as high as 23 million people, according to Adelheid Marschang, a senior emergencies officer with the World Health Organisation.
"This is a crisis on top of multiple crises in the affected region," Mr Marschang said in Geneva.
Those without homes to return to huddled in shopping malls, stadiums, mosques and community centres, while others spent the night outside in blankets gathering around fires, as search teams and emergency aid from around the world poured into the region. Rescuers working in freezing temperatures dug – sometimes with their bare hands – through the remains of buildings.
With the damage spread over a wide area, the massive relief operation often struggled to reach devastated towns, and voices that had been crying out from the rubble fell silent.
"We could hear their voices, they were calling for help," said Ali Silo, whose two relatives could not be saved in the Turkish town of Nurdag.
Nurgul Atay said she could hear her mother's voice beneath the rubble of a collapsed building in the Turkish city of Antakya, the capital of Hatay province, but that her and others' efforts to get into the ruins had been futile without any 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."
But in the north-western Syrian town of Jinderis, a young girl called Nour was pulled alive from the wreckage of a collapsed building on Monday.
A rescuer cradled her head in his hands and tenderly wiped dust from around her eyes as she lay amid crushed concrete and twisted metal before being pulled out and passed to another man.
Some relatives of victims of the disaster reported receiving voice notes from their loved ones, begging to be rescued. A team of experts from the UK has been sent to contribute to the rescue work, the UK Government has said.
Among them are Watch Commander John Aitchison from the Scottish Fire and Rescue Training Centre in Portlethan, Crew Commander Steven Adams, of MacAlpine Road Fire Station in Dundee, and firefighters Tony Armstrong and Keith Gauld, from Aberdeen’s North Anderson Drive Fire Station.
Bruce Farquharson, deputy assistant chief officer for the Scottish Fire and Rescue Service, said: “The scenes in Turkey and Syria are devastating and our thoughts are firmly with the families, friends and communities who have been affected by these tragic earthquakes.
“Our team will use their specialist skills and a range of technical equipment as they join a wider collective effort in a bid to save lives and they will also be supporting other emergency service teams already in the area.”
Prime Minister Rishi Sunak said the UK was working to send help to the region “as quickly as possible”.
"It’s obviously an incredibly tragic situation that we’re all seeing in Turkey and Syria,” he said. “I want everyone to know that we are doing what we can to provide support, we are in touch with the authorities in both Syria and Turkey.”
Rescue efforts are continuing in the region, where freezing conditions are making it more difficult for aid workers, particularly in rebel-held Syria, where people have fewer resources and there is a lack of routes to deliver aid through.
The United Nations said it was "exploring all avenues" to get supplies to rebel-held north-western Syria, where millions live in extreme poverty and rely on humanitarian aid to survive.
Philippe Leclerc, UNHCR representative in Turkey, said: “The situation is tragic, and we are witnessing it every day on the ground in the ten provinces which are affected by the earthquakes.
"We are witnessing again the disastrous effect of it on the lives of families, be they Turkish [or others], of course – because these ten regions are also hosting the largest refugee population in the world.”
Sebastien Gay, the head of mission in the country for Doctors Without Borders, said health facilities were overwhelmed, with medical personnel working around "around the clock to respond to the huge numbers of wounded".
The affected area in Syria is divided between government-controlled territory and the country's last opposition-held enclave, which is surrounded by Russian-backed government forces.
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 north-west Turkey in 1999.
The US Geological Survey measured Monday's quake at 7.8, with a depth of 11 miles. Hours later, another quake, likely triggered by the first, struck more than 60 miles away with 7.5 magnitude.