A magnitude-7.8 tremor has struck off the Pacific coast of Ecuador. Officials say at least 77 people are dead.

The US Geological Survey said Saturday's quake was centered just off the coast, at a shallow depth of 19 kilometers. There's damage near the epicenter, as well as in the largest city of Guayaquil.

The earthquake was Ecuador's worst in decades, and officials say the death toll is likely to rise. President Rafael Correa declared a national emergency and urged the public to stay calm.

The Pacific Tsunami Warning Center said tsunami waves up to 1 meter above the tide level are possible for some coasts of Ecuador. Neighboring Peru has also issued a tsunami alert for the north of the country.