Turkish President Recep Tayyip Erdogan visits the disaster zone in his country as criticism grows over the official response
Families in some badly-hit areas have said the slow speed of rescue efforts means they have had no help digging to find relatives
President Erdogan defends the response, saying it's not possible to prepare for disasters of this magnitude
More than 12,000 people in southern Turkey and northern Syria are now known to have been killed in Monday's earthquakes
Erdogan acknowledged there'd been difficulties with the initial response but blamed delays on damaged roads and airports
In Syria, the White Helmet group who are leading efforts to rescue people in rebel-held areas, say time is running out to save people
Dramatic footage and pictures are continuing to emerge of rescues in both countries
The confirmed death toll in Turkey has now risen to 2,921, says the head of the country's disaster and emergencies agency.
Yunus Sezer adds that another 15,834 people have been injured.
New drone footage shows the massive destruction in Turkey's border province of Hatay.
Plumes of smoke can be seen billowing from flattened buildings as rescue workers climb over collapsed structures looking for survivors.
Turkey and Syria earthquake: Drone footage shows Turkey earthquake aftermath
Image source, EPAIf you're just joining us - here's the latest:
Image source, EPAAlice Cuddy
Reporting from Istanbul
Here at Istanbul airport hundreds of people are gathered in one small area.
Onlookers told us the people had come here to volunteer to help with the earthquake response, with many presumably wanting to travel onwards to the most badly hit areas of the country.
The BBC has been unable to verify if everyone pictured is hoping to volunteer, but the scale of the crowds is certainly unusual.
More now on the US pledge to assist the ongoing search and rescue operation in Turkey.
The US Ambassador to Turkey, Jeff Flake, said two units would be deployed.
"One from Fairfax County [Virginia] and another from Los Angeles - what they call these heavy units, each with, I think, 70 personnel with search dogs as well as paramedics,” Flake told CNN.
“That’s what we are told is needed.”
The ambassador added: "Look at the scope of devastation. It's daunting."
He said that in the coming weeks a key challenge would also be to "find housing for those who cannot go back in their apartment buildings."
US President Joe Biden spoke earlier to his Turkish counterpart Recep Tayyip Erdogan, reaffirming "the readiness of the United States to provide any and all needed assistance".
In a statement, the White House said Biden "noted that US teams are deploying quickly to support Turkish search and rescue efforts and co-ordinate other assistance that may be required by people affected by the earthquakes, including health services or basic relief items".
It provided no further details about when and how many US rescuers would be deployed to the country.
At least 2,379 people were killed and 14,483 were injured in Turkey following the earthquakes, the country's vice-president says.
Fuat Otkay adds that 7,840 people were pulled alive from the rubble after 4,748 buildings were destroyed.
At least 1,444 people are reported to have died in Syria.
It means the death toll from the devastating earthquakes now stands at more than 3,500, but this is almost certain to rise as the rescue efforts continue.
The World Health Organization (WHO) earlier warned that the death toll could eventually rise eight-fold.
US President Joe Biden will speak "very soon" to his Turkish counterpart Recep Tayyip Erdogan, the White House says.
“We will certainly have a readout when that conversation occurs,” White House spokeswoman Karine Jean-Pierre said, without providing further details.
Earlier on Monday, Biden said he was "deeply saddened by the loss of life and devastation" caused by the earthquakes.
"I have directed my team to continue to closely monitor the situation in co-ordination with Turkey and provide any and all needed assistance," he tweeted.
Anna Foster
Reporting from Osmaniye, Turkey
Many sit out on the street as they are too scared to go home tonight
I’m in Osmaniye, southern Turkey, close to the epicentre of the devastating earthquake. I can see piles of rubble everywhere on the street and broken glass where shop fronts used to be.
Many of the roads into Osmaniye were closed. The tarmac was broken and bridges had collapsed.
I’ve spoken with a family who are staying near a makeshift fire on the street this evening, as they are too scared to return inside.
Each time we feel an aftershock, they move closer into the street.
It's pouring with rain, which is hampering rescue efforts in the town.
Some people in the city of Kahramanmaras in Turkey have been made homeless after the earthquake that struck the country this morning.
Gathered around a campfire to try and keep warm, one woman said they had nowhere to go: "We don't even have a bed."
Another man said his family hadn't eaten since this morning.
Image source, EPABuildings across Turkey have collapsed as a result of the earthquakes
The leader of a charity which works to remove landmines from conflict areas has described the moment he witnessed a devastating earthquake while trying to leave Turkey on Monday morning.
Damian O'Brien, who leads the Syria programme for the Halo Trust, was waiting for a flight in the Turkish town of Antakya, 20 miles north-west of the Syrian border, when the first earthquake struck.
"I'd just sat down in a departure lounge when the earthquake hit... The building started to move and people started running for the exits," he told BBC Radio 4's PM programme.
He managed to get the automatic doors of the airport open with the help of a Turkish woman, but says "it was clear the airport was out of action".
Quote MessageThe runway was breaking up in front of me, I saw the noses of the planes rising up on the runway like the front of some boats on an ocean and then they started to topple.
Damian O'Brien, Halo Trust in Syria
"A large metal canopy over the entrance to the terminal building had collapsed, and unfortunately there were some serious casualties."
Specialist rescue teams from countries all over the world are flying out to Turkey to help find survivors in the rubble.
Many are sending specialist firefighters, medics, equipment and specially trained dogs.
Image source, ReutersMembers of Germany's International Search and Rescue (ISAR) are ready to leave from Cologne-Bonn airport
Image source, EPA-EFE/REX/ShutterstockSwiss rescuers and service dogs gather at Zurich Airport
Image source, EPA-EFE/REX/ShutterstockFifty members of Hungary's HUNOR rescue team prepare to leave from Budapest
Image source, EPA-EFE/REX/ShutterstockMembers of a Greek rescue mission board a military plane
Mohammad Hamza, a co-ordinator for the aid agency Islamic Relief, was in the small town of Ad Dana in north-west Syria when the earthquake struck in Turkey this morning.
Hamza, a father of three, described the moment of panic when he felt the quake.
“I found my children were sleeping, I didn’t know what to do. Shall I wake them up or shall I leave them sleeping?" he told the BBC World Service's Newshour programme.
“We are dying anyway! This is what I was thinking. Shall I let them be scared by the situation?
Quote MessageIs it going to be better under the bed? Actually, I didn’t know what to do. I just froze, I stopped, I couldn’t move."
Mohammad Hamza, Co-ordinator, Islamic Relief aid agency
Pallab Ghosh
Science correspondent
The earthquake which first hit near Gaziantep on Monday was estimated to be 7.8, classified as "major", on the official magnitude scale. Its centre was relatively shallow at about 18km (11 miles), causing serious damage to buildings on the surface.
Prof Joanna Faure Walker, head of the Institute for Risk and Disaster Reduction at University College London, said: "Of the deadliest earthquakes in any given year, only two in the last 10 years have been of equivalent magnitude, and four in the previous 10 years."
But it is not only the power of the tremor that causes devastation.
Image source, .This incident occurred in the early hours of the morning, when people were inside and sleeping. The sturdiness of the buildings is also a factor.
Dr Carmen Solana, reader in volcanology and risk communication at the University of Portsmouth, says: "The resistant infrastructure is unfortunately patchy in south Turkey and especially Syria, so saving lives now mostly relies on response.
"The next 24 hours are crucial to find survivors. After 48 hours, the number of survivors decreases enormously."
Image source, Getty ImagesThousands of buildings in Syria were damaged by the quake, as seen here in Idlib
The latest death toll from this morning's devastating quakes has now exceeded 3,000 in Turkey and Syria, according to reports.
Some 2,316 people have now died in Turkey, according to the country's disaster agency.
In neighbouring Syria, at least 1,293 people have died, according to the government and rescue groups cited by the AFP news agency.
It reports that in government-controlled areas, Syria's health ministry says 593 people have now died. In rebel-held parts of the country's north-west, at least 700 people were killed, according to the White Helmets rescue group, as quoted by AFP.
Image source, ReutersThe image of Raghad Ismail being carried away from the rubble was captured on video earlier today
Earlier, we showed you dramatic images of a Syrian toddler pulled from the rubble of a collapsed building and being rushed from the scene by her rescuer.
We've since learned that the 18-month-old, whose name is Raghad Ismail, is now safe and with her uncle in his home in Azaz.
The man who gave his name as Abu Hussam spoke to Reuters news agency about what happened to the rest of the family.
Most of them did not make it out alive.
"The father is feared to have his back broken... His pregnant wife, his five-year-old daughter and his four-year-old son have all been killed.”
Image source, ReutersRaghad Ismail is now with her uncle Abu Hussam in north-west Syria
Laura Gozzi
BBC News Live reporter
Image source, ReutersYou may have come across people on social media who claim they either "predicted" today's earthquake or that they are certain another one is about to occur.
It is worth remembering that despite remarkable advances in the field of seismology, there is no scientific basis for earthquake predictions. There is always a chance for earthquakes in places with active faults, such as the Turkey-Syria border, but predicting an earthquake with a high level of precision is extremely difficult, because of the variation in geology and other factors that are unique to each location.
Precursor tremors, release of a gas called radon and toad behaviour have all been used to attempt to look for signals that indicate a large earthquake is about to happen, with variable success.
Dr Dan Faulkner, senior lecturer in rock mechanics at the University of Liverpool, previously told the BBC that some quakes have no warning signs: "Detailed scientific research has told us that each earthquake displays almost unique characteristics, preceded by foreshocks or small tremors, whereas others occur without warning. There simply are no rules to utilise in order to predict earthquakes.
"Earthquake prediction will only become possible with a detailed knowledge of the earthquake process. Even then, it may still be impossible."
Read more here.
Extensive search-and-rescue operations are continuing in Turkey and Syria following two earthquakes on Monday.
Middle East correspondent Anna Foster reports on the rescue efforts in Adana, Turkey - one of the cities hit by the quakes.
Lyse Doucet
Chief International Correspondent
Image source, EPA-EFE/REX/ShutterstockSyria has been shaken by nature’s powerful force at a time when this country is already broken, worn down by more than a decade of war, fractured into government and rebel-held areas.
One of the worst affected regions is Idlib, the last opposition-held enclave in the north, along the Turkish border.
Even before this disaster, it was one of the hardest parts of the world for aid agencies to reach: there’s only one small crossing, through Bab al-Hawa, on the Turkish border.
It’s the only lifeline allowed by the Syrian government, which controls most of the country, and its Russian ally. Now, this area of Syria is in even more urgent need of help - with some four million people who were already living on the edge, in flimsy makeshift shelters in freezing winter temperatures.
Mark Kaye of the International Rescue Committee appealed for politics to be left out of aid: "The international community needs to show solidarity here, and this is an important reminder, you know, this is [a] crisis, within a crisis, within a crisis. Just this week, we were already warning of freezing temperatures about to hit the region.”
The Syrian government is also appealing for help - every part of Syria has been left impoverished and exhausted by war.
Now President Bashar al-Assad may need to look to Western countries and neighbours he often condemned for backing his enemies to help him against a powerful force of nature which knows no politics.
The death toll in Turkey from this morning's earthquake has risen again to 1,762, according to the country's disaster management agency.
The combined death toll from the initial quake in Turkey and Syria is now believed to be more than 2,700 after at least 1,000 people were reported to have been killed in Syria.