Rescuers scoured debris in a desperate search for survivors on Friday four days after a massive earthquake hit Turkey and Syria, killing nearly 22,000 people, as the United States offered an $85-million aid package.
The first UN aid deliveries arrived on Thursday in Syrian rebel-held zones, but chances of finding survivors have dimmed since the passing of the three-day mark that experts consider a critical period to save lives.
The US Agency for International Development said its aid package will go to partners on the ground "to deliver urgently needed aid for millions of people", including through food, shelter and emergency health services.
It will also support safe drinking water and sanitation to prevent the outbreak of disease, USAID said in a statement.
Bitter cold hampered search efforts in both countries, but more than 80 hours after the disaster struck, 16-year-old Melda Adtas was found alive in the southern Turkish city of Antakya.
Her overjoyed father was in tears and the grieving nation cheered an agonisingly rare piece of good news.
"My dear, my dear!" he called out as rescuers pulled the teen out of the rubble and the watching crowd broke into applause.
The 7.8-magnitude quake struck early Monday as people slept, in a region where many had already suffered loss and displacement due to Syria's civil war.
Top aid officials were planning to visit affected areas with World Health Organization head Tedros Adhanom Ghebreyesus and UN humanitarian chief Martin Griffiths both announcing trips.
The president of the International Committee of the Red Cross, Mirjana Spoljaric, travelled to strife-torn Aleppo, Syria.
"Communities struggling after years of fierce fighting are now crippled by the earthquake," Spoljaric tweeted.
"As this tragic event unfolds, people's desperate plight must be addressed".
An aid convoy crossed the Turkish border into rebel-held northwestern Syria on Thursday, the first delivery into the area since the quake, an official at the Bab al-Hawa crossing told AFP.
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.
UN Secretary-General Antonio Guterres urged the Security Council to authorise the opening of new cross-border humanitarian aid points between Turkey and Syria.
Four million people living in the rebel-held areas have had to rely on the Bab al-Hawa crossing as part of an aid operation authorised by the UN Security Council nearly a decade ago.
"This is the moment of unity, it's not a moment to politicise or to divide but it is obvious that we need massive support," Guterres said.
Temperatures in the Turkish city of Gaziantep, located near the epicentre of the quake, plunged to minus three degrees Celsius (26 degrees Fahrenheit) early on Friday.
Despite the cold, thousands of families had to spend the night in cars and makeshift tents - too scared or banned from returning to their homes.
Parents walked the streets of the city carrying their children in blankets because it was warmer than sitting in a tent.
Gyms, mosques, schools and some stores have opened at night. But beds are scarce and thousands spend the nights in cars with engines running to provide heat.
"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.
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 18,342 people had died in Turkey and 3,377 in Syria from Monday's tremor, bringing the confirmed total to 21,719.
Experts fear the number will continue to rise sharply.
Anger has mounted over the government's handling of the disaster.
"People who didn't die from the earthquake were left to die in the cold," Hakan Tanriverdi told AFP in Adiyaman province, one of the areas hardest hit.
On a visit to the area, Turkish President Recep Tayyip Erdogan admitted there had been "shortcomings" in the government's handling of the disaster.
In the devastated Turkish town of Nurdagi, close to the epicentre, emergency workers using drones and heat detecting monitors ordered silence when a potential survivor was found.
"The quiet is agonising. We just don't know what to expect," Emre, a local resident, said as he waited next to one block on a main road into the town.
Dozens of nations have pledged to help. The World Bank said it would give $1.78 billion in aid to Turkey to help relief and recovery efforts.
Immediate assistance of $780 million will be offered from two existing projects in Turkey, said the bank, while an added $1 billion in operations is being prepared to support affected people.
In addition to a staggering human toll, the quake's economic cost appears likely to exceed $2 billion and could surpass $4 billion, Fitch Ratings said.