“We were preparing to transmit a local football game when everything started to shake and the people fled in panic,” he said of a game in Portoviejo. “I had to to avoid being crushed by the people. I have some scrapes. But what I see around me is really terrible, startling and very sad.”

Ecuador has a history of destructive earthquakes, but the one on Saturday, which by some accounts lasted more than a minute, is believed to have been one of the most powerful since the 1970s. Some geologists said its force was 20 times greater than the deadly earthquake that struck southern Japan early Saturday.

The quake had a depth of nearly 12 miles. Several aftershocks, some as strong as magnitude 5.6, followed. The earthquake’s center was 16 miles southeast of Muisne, Ecuador, the United States Geological Survey said.

About 4,600 members of the National Police and 10,400 members of the armed forces were mobilized as part of the emergency response. Hundreds of doctors, health professionals and rescue workers were heading toward the hardest-hit areas.

The president’s emergency decree gives the government expanded authority and a state of emergency in six of the country’s 24 provinces. Deaths were reported in the northern provinces of Esmeraldas, Manabí and Guayas.

Among the dead were a youngster who fell down the stairs in a mall in the southern port city of Guayaquil and another who died after the collapse of a bridge in the city, according to reports from the television station Teleamazonas.