A powerful, 7.8-magnitude earthquake has shaken Ecuador's northwest Pacific coast, killing at least 233 people and spreading panic.

The US Geological Survey said the shallow quake, the strongest in decades to hit Ecuador, was centred 27km south-southeast of Muisne, a sparsely populated area of fishing ports popular with tourists.

"The official figure of the number killed has risen to 233," President Rafael Correa said on his Twitter account on Sunday. Officials had previously put the toll of Saturday's quake at 77 dead and nearly 600 injured.

The quake caused "considerable damage" near the epicentre as well as in Guayaquil, the country's most populous city.

Residents streamed into the streets of the capital Quito, hundreds of miles away, and other towns across the nation.

The country's Geophysics Institute in a bulletin said the quake struck at around 8pm (01:00 GMT) at a depth of 20km.

Among those killed was the driver of a car crushed by an overpass that buckled.

On social media residents shared photos of homes collapsed, the roof of a shopping centre coming apart and supermarket shelves shaking violently.

The location of the 7.8-magnitude earthquake, according to US Geological Survey [EPA]

In Manta, the airport was closed after the control tower collapsed, injuring an air force official. Hydroelectric dams and oil pipelines in the OPEC-member nation were shut down as a precautionary measure.

The Pacific Tsunami Warning Center said hazardous tsunami waves are possible for some coasts but the government has not issued a tsunami alert.

Towns near the epicentre were being evacuated as a precautionary measure.

An emergency had been declared in six provinces.

Later on Sunday, a magnitude 6.1 earthquake struck southeast of the Pacific island nation of Tonga.

Earlier, two deadly earthquakes hit the southernmost of Japan's four main islands.

A magnitude-6.5 earthquake struck Thursday near Kumamoto, followed by a magnitude-7.3 earthquake just 28 hours later.

The quakes have killed 41 people and injured about 1,500, flattened houses and triggered major landslides.

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Source: Agencies