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

The U.S. Geological Survey said the shallow quake, the strongest in decades to hit Ecuador, was centered 16 miles southeast of Muisne, in a sparsely populated area of fishing ports that's popular with tourists.

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 country's most populous city, hundreds of miles from the earthquake's epicenter.

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

In Manta, the airport was closed after the control tower was severely damaged.

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

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

While the government hadn't issued a tsunami alert, Glas urged residents along the coast to move to higher ground. Towns near the epicenter were also being evacuated as a precautionary measure. An emergency had been declared in six provinces, he said.

“It's very important that Ecuadoreans remain calm during this emergency,” Glas said.

In the capital, the quake was felt for about 40 seconds and people fled to the streets in fear.

Quito is located about 105 miles from the temblor's epicenter. The quake knocked out electricity and cellphone coverage in several neighborhoods in the capital.

“I'm in a state of panic,” said Zoila Villena, one of many Quito residents who congregated in the streets. “My building moved a lot and things fell to the floor. Lots of neighbors were screaming and kids crying.”

The U.S. Geological Survey originally put the quake at a magnitude of 7.4 then raised it to 7.8.