President Rafael Correa rushed home from a trip to Italy to supervise the emergency. "The immediate priority is to rescue people in the rubble," he said on Twitter.
"Everything can be rebuilt but lives cannot be recovered and that's what hurts the most," Correa told state radio.
The government said 262 people were killed and up to 2,500 injured, according to the latest tallies on April 17 evening.
Coastal areas nearest the epicenter were hit hardest, especially Pedernales, a rustic tourist spot with beaches and palm trees now laden with debris from pastel-colored houses.
Dazed residents recounted a violent shake, followed by a sudden collapse of buildings that trapped people in wreckage.
Authorities said there were more than 160 aftershocks, mainly in the Pedernales area. A state of emergency was declared in six provinces.
The quake has piled pain on the economy of OPEC's smallest member, already reeling from low oil prices, with economic growth this year projected at near-zero.
RUBBLE, RAIN, DARKNESS
As darkness set in and rain began, survivors bundled up to spend the night next to their destroyed homes. Many had earlier queued up for food, water and blankets outside the blue-and-white stadium.
Inside the stadium, tents housed the dead and medical teams treated hundreds of survivors. About 91 people died in Pedernales and some 60 percent of houses were destroyed, according to Police Chief General Milton Zarate.
Locals used a small tractor to remove rubble and also searched with their hands for trapped people. Women cried after a corpse was pulled out.
In Guayaquil, Ecuador's largest city, rubble lay in the streets and a bridge fell on top of a car.
About 13,500 security force personnel were mobilized to keep order around Ecuador, and US$600 million in credit from multilateral lenders was immediately activated for the emergency, the government said.
