According to Ecuador's emergency response services, victims suffered head and other wounds and at least 135 homes were damaged in the shake, which was felt as far away as the capital Quito.

Fisherman Andres Mafare, aged 36, was walking to the port when he heard a loud crack followed by a strong earthquake that shook overhead cables.

He raced home to try to find his wife and two sons. "I ran like crazy, and when I got here saw that my house had been destroyed," he told AFP.

An AFP reporter in Esmeraldas witnessed tumbled-down walls, facades that had collapsed onto a road in a pile of debris and several cracked buildings.

Families stood around surveying the damage.

"It was very strong," former presidential candidate Yaku Perez told AFP from the scene.

"It felt like an eternity, but I guess it was less than a minute."

The authorities said four health centers and 18 schools had been damaged, while the facade of a military building partially collapsed. Two roads and a bridge were also damaged.

According to official estimates, about 80 percent of homes were left without power or phone access.

National oil company Petroecuador said it briefly "suspended operations" at the Esmeraldas refinery and a nearby pipeline.

The refinery produces 111,000 barrels a day and the Transecuadorian Pipeline System transports 360,000 barrels a day.

Daniel Noboa, the South American nation's newly re-elected president, said he was rushing ministers to the scene to help coordinate the building of shelters and delivery of humanitarian aid.

"The government is with you, and that's how it will be going forward," he said on social media.

The US Geological Survey and local monitors said the quake struck just off the coast at a depth of about 35 kilometers (22 miles) shortly before 7:00 am local time (1200 GMT).

Ecuadoran authorities said there was no tsunami risk from the quake.

Ecuador sits on one of the most geologically active zones on Earth, and the fault between the Nazca and South American plates runs along its coast.

The Geophysical Institute said that "the convergence of the Nazca and South American plates, which have a movement speed of 5.6 centimeters (2.2 inches) per year, is the process that generates the largest earthquakes in the country."

The tremor was felt in 10 of the country's 24 provinces.

There were no reports of injuries across the border in neighboring Colombia.

Last week, Ecuador marked the anniversary of the 2016 earthquake that struck the coasts of Manabi and Esmeraldas. With a magnitude of 7.8, it left 673 dead and about 6,300 injured.