Rescue and relief efforts focused on the city of Van and the town of Ercis, 100km to the north, but hundreds were also feared dead in remote villages of mud-brick houses after Sunday's 7.2 magnitude quake, Turkey's strongest in a decade.
Thousands of people made homeless by the quake were forced to spend a second night outdoors in the hilly, windswept Van region, enduring near-freezing temperatures.
The U.N. disaster agency said almost 1,000 buildings had collapsed, many of them poorly built. A Red Crescent spokesman said the agency was preparing to provide refuge for as many as 40,000 people, though it was so far impossible to tell how many would need shelter.
Some residents of Van and outlying villages complained of a lack of government assistance, despite the dispatch of troops, mobile kitchens and up to 13,000 tents.
The hardest-hit town was Ercis, a town of 100,000, where 55 buildings crumpled, including a student dormitory.
The Red Crescent has delivered 5,000 tents to Ercis alone and a tent city has been set up at Ercis stadium. But residents said tents were being given only to relatives of police and soldiers, a possible source of tension if confirmed.
Rescue efforts were hampered by power outages after the quake toppled electricity lines to towns and villages.
More than 200 aftershocks have jolted the region since the quake, lasting around 25 seconds, struck at 1041 GMT Sunday.
The Red Crescent said about 100 experts had reached the earthquake zone to co-ordinate rescue and relief operations. Sniffer dogs had joined the quest for survivors.
Major geological fault lines cross Turkey, where small tremors occur almost daily. Two large quakes in 1999 killed more than 20,000 people in the northwest.