President Rafael Correa said the death toll will "certainly" rise in the 7.8-magnitude quake that struck the small, oil-producing South American nation late Saturday.
The quake, the most powerful to strike Ecuador in decades, shattered hotels and homes along its Pacific coast popular with tourists and reduced several towns to rubble.
More than 2,000 people were injured as structures tumbled during the quake or its dozens of aftershocks.
The capital Quito, farther inland, escaped with cracked walls and power outages, and the country's strategic oil facilities appeared unscathed, officials said.
In Portoviejo, a city 15 kilometres from the coast, the temblor knocked down walls in a prison, allowing 100 inmates to escape.
Some were recaptured or returned later, but police were hunting for the others, Justice Minister Ledy Zuniga tweeted.
Elsewhere in hard-hit Portoviejo, the stench of decaying bodies began to fill the tropical air as rescuers raced to find survivors.
"We have already recovered three dead and we believe there are 10 to 11 people still trapped," said one worker digging through the debris of what used to be a six-story hotel called El Gato.
President Correa visited the disaster zone yesterday after cutting short an official trip to the Vatican.
He said the latest toll of 272 dead "will certainly rise and probably in a considerable way" in the hours ahead.
"There are still lots of bodies in the rubble," he warned. "These are extremely difficult times, the biggest tragedy in the last 67 years."
Correa made reference to the August 1949 earthquake near the central Ecuadoran city of Ambato that killed some 5,000 people and caused widespread destruction.
