Hopes faded Thursday of finding more survivors after the earthquake that killed nearly 20,000 people in Turkey and Syria, as the first UN aid reached Syrian rebel-held zones.
Bitter cold has hampered the four-day search of thousands of flattened buildings and threatened the lives of many quake victims who are without shelter and drinking water.
Relatives were left scouring body bags laid out in a hospital car park in Turkey's southern city of Antakya to search for missing relatives, an indication of the scale of the tragedy.
"We found my aunt, but not my uncle," said Rania Zaboubi, a Syrian refugee who lost eight members of her family as other survivors sought loved ones' bodies.
Chances of finding survivors have dimmed now that the 72-hour mark that experts consider the most likely period to save lives has passed.
The 7.8-magnitude quake struck as people slept early Monday in a region where many people had already suffered loss and displacement due to Syria's civil war.
But in a potentially life-saving development, an aid convoy reached rebel-held northwestern Syria on Thursday, the first since the quake, an official at the Bab al-Hawa border crossing told AFP.
- Freezing temperatures -
The aid passage through the crossing is the only way UN assistance can reach civilians without going through areas controlled by Syrian government forces.
A decade of civil war and Syrian-Russian aerial bombardment had already destroyed hospitals, collapsed the economy and prompted electricity, fuel and water shortages.
Temperatures in the Turkish city of Gaziantep plunged to minus five degrees Celsius (23 degrees Fahrenheit) early Thursday, but thousands of families spent the night in cars and makeshift tents -- too scared or banned from returning to their homes.
Parents walked the streets of the city -- close to the epicentre of Monday's earthquake -- carrying their children in blankets because it was warmer than sitting in a tent.
Some people have found sanctuary with neighbours or relatives. Some have left the region. But many have nowhere to go.
Gyms, mosques, schools and some stores have opened at night. But beds are still at a premium and thousands spend the nights in cars with engines running to provide heat.
"When we sit down, it is painful and I fear for anyone who is trapped under the rubble in this," said Melek Halici, who wrapped her two-year-old daughter in a blanket as they watched rescuers working into the night.
International rescuers have said the intense cold has forced them to weigh whether to use their limited fuel supplies to keep warm or to carry out their work.
- Racing against the clock -
"Not a single person has failed to mention this, the cold," Athanassios Balafas, a Greek fire official, said in Athens. "Obviously we chose to keep operating."
Turkish President Recep Tayyip Erdogan, after mounting criticism online, acknowledged on Wednesday "there are shortcomings. The conditions are clear to see. It's not possible to be ready for a disaster like this."
Monday's quake was the largest Turkey has seen since 1939, when 33,000 people died in the eastern Erzincan province.
Officials and medics said 16,546 people had died in Turkey and 3,317 in Syria from Monday's 7.8-magnitude tremor, bringing the confirmed total to 19,863. Experts fear the number will continue to rise sharply.
Despite the dimming hopes for rescues, thousands of local and foreign searchers have not given up in the hunt for more survivors.
Two dozen children and some of their parents from northern Cyprus -- 39 Turkish Cypriots in all -- were on a school trip to join a volleyball tournament when the quake hit their hotel in southeast Turkey's Adiyaman.
Their home region's government has declared a national mobilisation, hiring a private plane so they could join the search-and-rescue effort for the children.
Ilhami Bilgen, whose brother Hasan was on the volleyball team, looked at the frightening pile of concrete slabs and heavy bricks that used to be the hotel.
- Donor conference -
"There's a hollow over there. The children may have crawled into it," Bilgen said. "We still haven't given up hope."
Dozens of nations, including China and the United States have pledged to help, and search teams as well as relief supplies have already arrived.
In Brussels, the EU is planning a donor conference in March to mobilise international aid for Syria and Turkey.
The European Union said the conference would be held in coordination with Turkish authorities "to mobilise funds from the international community in support for the people" of both countries.
The bloc was swift to dispatch rescue teams to Turkey after the massive 7.8-magnitude earthquake struck the country on Monday close to the border with Syria.
But it initially offered only minimal assistance to Syria through existing humanitarian programmes because of EU sanctions imposed since 2011 on the government of President Bashar al-Assad in response to his brutal crackdown on protesters, which spiralled into a civil war.
In addition to a staggering human toll, the quake's economic cost appears likely to exceed $2 billion and could reach $4 billion or more, Fitch Ratings said.