The Syrian regime has been criticised for bombing a town shortly after it was hit by the earthquake that has claimed nearly 8,000 lives and rising.
Britain’s Foreign Secretary James Cleverly criticised the Assad regime for the "completely unacceptable bombing" of an opposition-held area in Syria in the immediate aftermath of the earthquake.
Conservative MP Alicia Kearns, who chairs the Commons Foreign Affairs Committee, said of Bashar Assad's regime: "Yesterday he bombed Marea, which was an area affected by the earthquake, in what was a truly callous and heinous attack and opportunism for him to try and attack and destroy the moderate opposition."
Mr Cleverly replied: "(Ms Kearns) is absolutely right to highlight the completely unacceptable bombing of areas in the immediate aftermath of this natural disaster.
"Sadly it speaks to a long-standing pattern of behaviour by the Assad regime, a regime that we condemn, have sanctioned and will continue to bring about sanctions - working with our international friends and partners - to try and prevent behaviour like this occurring again."
Time is running out for the survivors of the devastating earthquakes that hit Turkey and Syria and who are trapped in the rubble as the death toll passed 7,800 today.
The World Health Organisation has warned the toll could climb as high as 20,000.
Rescuers toiled through the night searching for survivors, with efforts continuing today, as emergency services from other countries flew in to join them.
In the Turkish city of Antakya, capital of Hatay province near the Syrian border, a woman's voice was heard calling for help under a pile of rubble.
The body of a small child lay lifeless nearby.
Weeping in the rain, a resident who gave his name as Deniz wrung his hands in despair.
"They're making noises but nobody is coming," he said. "We're devastated, we're devastated. My God... They're calling out. They're saying, 'Save us' but we can't save them. How are we going to save them? There has been nobody since the morning."
Families slept in cars lined up in the streets.
Ayla, standing by a pile of rubble where an eight-storey building once stood, said she had driven to Hatay from Gaziantep on Monday in search of her mother.
Five or six rescuers from the Istanbul fire department were working in the ruins.
"There have been no survivors yet. A street dog came and barked at a certain point for long, I feared it was for my mother. But it was someone else," she said.
Also in Antakya, Nurgul Atay told how she could hear her mother's voice beneath the rubble of a collapsed building, 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.”
The magnitude 7.8 quake - the deadliest in Turkey since 1999 - hit early on Monday and was followed by a second hours later.
Thousands of buildings were toppled, hospitals and schools wrecked and tens of thousands of people were injured or left homeless in several Turkish and Syrian cities.
Turkish President Tayyip Erdogan on Tuesday declared a state of emergency in 10 provinces
A day after the quakes hit, rescuers working in harsh conditions struggled to dig people out of the rubble of collapsed buildings.
As the scale of the disaster became ever more apparent, the death toll looked likely to rise considerably. One United Nations official said it was feared thousands of children may have been killed.
"There is not even a single person here. We are under the snow, without a home, without anything," said Murat Alinak, whose home in Malatya had collapsed and whose relatives are missing. "What shall I do, where can I go?"
Monday's magnitude 7.8 quake, followed hours later by a second one almost as powerful, toppled thousands of buildings including hospitals, schools and apartment blocks.
Tens of thousands of people were injured or left homeless in cities in Turkey and northern Syria.
Winter weather has hampered rescue and relief efforts and made the plight of the homeless even more miserable. Some areas were without fuel and electricity.
Aid officials voiced particular concern about the situation in Syria, already afflicted by a humanitarian crisis after nearly 12 years of civil war.
Erdogan on Tuesday declared 10 Turkish provinces a disaster zone and imposed a state of emergency there for three months. This will permit the government to bypass parliament in enacting new laws and to limit or suspend rights and freedoms.
The government will open up hotels in the tourism hub of Antalya to temporarily house people impacted by the quakes, said Erdogan, who faces a national election in three months' time.
The death toll in Turkey rose to 5,434, Health Minister Fahrettin Koca said, adding that 31,777 people were injured. In Syria, the toll was at least 1,832, according to the government and a rescue service in the insurgent-held northwest.
Turkish authorities say some 13.5 million people were affected in an area spanning roughly 450 km (280 miles) from Adana in the west to Diyarbakir in the east, and 300 km from Malatya in the north to Hatay in the south.
Syrian authorities have reported deaths as far south as Hama, some 250 km from the epicentre.
"It's now a race against time," World Health Organization Director General Tedros Adhanom Ghebreyesus said in Geneva. "Every minute, every hour that passes, the chances of finding survivors alive diminishes."
Across the region, rescuers toiled night and day as people waited in anguish by mounds of rubble clinging to the hope that friends, relatives and neighbours might be found alive
In Antakya, capital of Hatay province bordering Syria, rescue teams were thin on the ground and residents picked through debris themselves. People pleaded for helmets, hammers, iron rods and rope.
One woman, aged 54 and named Gulumser, was pulled alive from an eight-storey building 32 hours after the quake.
Another woman then shouted at the rescue workers: "My father was just behind that room she was in. Please save him."
The workers explained they could not reach the room from the front and needed an excavator to remove the wall first.
More than 12,000 Turkish search and rescue personnel are working in the affected areas, along with 9,000 troops. Some 70 countries and sending personnel, equipment and aid.
But the sheer scale of the disaster is daunting.
"The area is enormous. I haven't seen anything like this before," said Johannes Gust, from Germany's fire and rescue service, as he loaded equipment onto a truck at Turkey's Adana airport.
Turkey's Disaster and Emergency Management Authority said 5,775 buildings had been destroyed in the quake and that 20,426 people had been injured.
In Geneva, UNICEF spokesperson James Elder said: "The earthquakes...may have killed thousands of children."
Syrian refugees in northwest Syria and in Turkey were among the most vulnerable people affected, Elder said.
In the Syrian city of Hama, Abdallah al Dahan said funerals for several families were taking place on Tuesday.
"It's a terrifying scene in every sense," said Dahan, contacted by phone. "In my whole life I haven't seen anything like this, despite everything that has happened to us."
Mosques opened their doors to families whose homes were damaged.
The Syrian state news agency SANA said at least 812 people were killed and 1,449 people injured in the government-held provinces of Aleppo, Latakia, Hama, Idlib and Tartous.
At least 1,020 people were killed in Syria's opposition-held northwest and 2,300 injured with the toll expected to "rise dramatically", the White Helmets rescue team said.
"There are lot of efforts by our teams, but they are unable to respond to the catastrophe and the large number of collapsed buildings," group head Raed al-Saleh said.
Time was running out to save hundreds of families trapped under the rubble of buildings and urgent help is needed from international groups, he said.
A U.N. humanitarian official in Syria said fuel shortages and the harsh weather were creating obstacles.
"The infrastructure is damaged, the roads that we used to use for humanitarian work are damaged," U.N. resident coordinator El-Mostafa Benlamlih told Reuters from Damascus.
A fire that engulfed hundreds of shipping containers at Turkey's Iskenderun port was put out, the defence ministry said, but it was not clear when operations there would resume.
In Malatya, Turkey, locals with no specialist equipment or even gloves tried to pick through the wreckage of homes crumpled by the force of the earthquake.
"My in-laws' grandchildren are there. We have been here for two days. We are devastated," said Sabiha Alinak.
"Where is the state? We are begging them. Let us do it, we can rescue them. We can do it with our means."