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.
And residents in several damaged Turkish cities voiced anger and despair at what they said was a slow and inadequate response from the authorities to the deadliest earthquake to hit Türkiye since 1999.
"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 Türkiye 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 has 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 Türkiye rose to 5434, Health Minister Fahrettin Koca said, adding that 31,777 people were injured. In Syria, the toll was at least 1832, according to the government and a rescue service in the insurgent-held northwest.