President Lenin Moreno said there were no immediate reports of victims or major damage from the quake, which jolted many Ecuadoreans who were still in bed shortly after 6 a.m. (1100 GMT). It was felt in 12 provinces across the country.
The U.S. Geological Survey said the quake, with a depth of 15.5 miles (25 kilometers), was centered around the town of San Vicente.
Authorities said that there wasn't a risk of a tsunami and appealed for calm.
They also expressed optimism that Ecuadoreans were better prepared for a natural disaster after rebuilding from last year's magnitude 7.8 quake along the Pacific coast that left more than 600 people dead and thousands more injured and homeless.
"We've made some giant steps and are much more prepared than we were in the past," said Ricardo Penaherrera, a top official with Ecuador's agency for risk management, pointing out that authorities carried out an earthquake drill last week in the same area where Sunday's quake took place.
He said authorities were still canvassing coastal areas for damage but that other than knocking out power in some rural areas there were no immediate reports of major damage.
Fabricio Diaz, governor of Manabi province, said emergency dispatchers received just 38 phone calls, the majority from residents inquiring about the quake's epicenter rather than reporting damages. The province's ports, dams and major roadways were unaffected, he said.
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