There have been desperate scenes as rescuers and family members searched for survivors, often with bare hands.
Teams from Switzerland, Spain and several Latin American countries have arrived to join the search effort.
More than 2,000 people were injured in the quake, Ecuador's most powerful in decades, which hit its Pacific coast.
Earlier, President Rafael Correa warned that the death toll was likely to rise, and said there were still people alive under the rubble of collapsed buildings. He said it was the biggest tragedy to hit Ecuador in the past seven decades.