Ecuador earthquake
At least 28 people were killed by in Ecuador quakeUSGS

At least 28 people have been killed when a powerful earthquake of magnitude 7.8 struck Ecuador. The South American country has declared a state of emergency in at least six provinces following the tremors.

The deadly quake set off panic as several houses were flattened and brought down a flyover. Ecuador's Vice President Jorge Glas said in a televised address that preventive measures are underway in coastal areas over fear of tsunami waves.

The US Geological Survey (USGS) said it was one of the strongest quakes to strike Ecuador in decades. The death toll in the shallow earthquake, which was centred in the coastal town of Muisne, is likely to rise further as reports of the extent of damage are still emerging.

"We have 16 people dead in the city of Portoviejo, 10 in Manta and two in the province of Guayas," said the vice president.

Several people have fled their homes in capital Quito. Power supply has been knocked out in several cities.

A 36-year old resident Lorena Casares told Reuters: "I was in my house watching a movie and everything started to shake. I ran out into the street and now I don't know what's going to happen." Social media images show cracks in the homes and businesses.

A bridge collapsed in Guayaquil, the country's most populous city, crushing a driver to death, local reports suggest.

"There is considerable damage in the area of the epicentre and also as far away as places like the city of Guayaquil," according to a bulletin issued by the Geophysics Institute.