A magnitude 6.2 earthquake has struck off the coast of Ecuador, the Pacific Tsunami Warning Center says, just days after a major quake hit the country killing nearly 500 people.

The quake was centred 70km west-southwest of Esmeraldas at a shallow depth of 10km, not far from the epicentre of Saturday's 7.8 magnitude quake.

Reuters witnesses in the zone said two strong tremors of about 30 seconds each were felt, waking people up and sending them racing them into the street.

It was not felt in the highland capital of Quito.

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There was no immediate word from authorities on the impact of Wednesday's quake.

- AAP