QUITO, Ecuador — A powerful, 7.8-magnitude earthquake shook Ecuador’s central coast Saturday, killing at least 28 people and spreading panic as far away as the capital, Quito, as it collapsed homes and rattled buildings.

The US Geological Survey said the shallow quake, the strongest in decades to hit Ecuador, was centered 16 miles south-southeast of Muisne, in a sparsely populated area of fishing ports that is popular with tourists. The quake had a depth of about 12 miles.

Vice President Jorge Glas said in a televised address that there were initial reports of 28 dead in the cities of Manta, Portoviejo, and Guayaquil. Among those killed was the driver of a car crushed by an overpass that buckled in Guayaquil, the city’s most populous city hundreds of miles from the epicenter.

On social media, photos showed homes collapsed, the roof of a shopping center coming apart, and supermarket shelves shaking violently. Aiports were closed in Manta and Guayaquil.

President Rafael Correa, who is in the Vatican after attending a papal conference, called on Ecuadoreans to show strength while authorities monitor events and respond to reports of injuries and damage.

The Pacific Tsunami Warning Center said tsunami waves were possible for some coasts.

While the government did not issue a tsunami alert, Glas urged residents along the coast to move to higher ground and towns near the epicenter were also being evacuated as a precaution. An emergency was declared in six provinces.

In the capital, the quake was felt for about 40 seconds and people fled to the streets in fear. Quito is about 105 miles from the quake’s epicenter. The quake knocked out electricity and cellphone coverage in several neighborhoods.

Several aftershocks, some as strong as 5.6 on the Richter scale, continued in the hour after the first quake, which occurred at nightfall.