Ecuador's strongest earthquake in decades, a 7.8 magnitude tremor, struck off the Pacific coast on Saturday, killing at least 41 people and causing damage near the epicenter as well as in the largest city of Guayaquil.
President Rafael Correa declared a national emergency and urged the Andean nation's 16 million people to stay calm.
"Our infinite love to the families of the dead," he said on Twitter, while cutting short a trip to Italy to return home.
Authorities urged people to evacuate coastal areas for fear of rising tides. Alarmed residents streamed into the streets of the highland capital Quito, hundreds of kilometers (miles) away, and other towns across the nation.
The government said the death toll would likely rise and damages were "serious", especially in the western coastal areas nearest the quake and in Guayaquil.
"Unfortunately, up to the moment there are 41 citizens who have lost their lives," said Vice President Jorge Glas, noting that it was the strongest quake to hit Ecuador since 1979.
The quake struck early evening at a depth of 20 km (12.4 miles), and was felt all around the country.
"There are villages that are totally devastated," said Gabriel Alcívar, mayor of the city of Pedernales in the hard-hit province of Manabi, in a radio interview. "What happened here in Pedernales is catastrophic."
Ramón Solorzano, 46, a car parts merchant in the city of Manta, said he was getting ready to leave the city with his family.
"Most people are out in the streets with backpacks on, heading for higher ground," he said, speaking in a trembling voice via a WhatsApp phone call. "The streets are cracked. The power is out and phones are down."
Parts of the capital were without power or telephone service, with many communicating only via WhatsApp. Photos on social media showed cracks in the walls of shopping centers.
The capital's municipal government later said power had been restored and there were no reports of casualties in the city.
The Pacific Tsunami Warning Center said tsunami waves reaching 0.3 to 1 meter (one to three feet) above tide level were possible for some coastal areas of Ecuador.
State officials said the OPEC nation's oil production was not affected by the quake but that the principal refinery of Esmeraldas, located near the epicenter, had been halted as a precaution.
Social media pictures showed a collapsed bridge in Guayaquil and minor damage to the lobby of a hotel, as well as images of a collapsed control tower at an airport in the city of Manta.
"At first it was light, but it lasted a long time and got stronger," said Maria Jaramillo, 36, a resident of Guayaquil, describing windows breaking and pieces falling off roofs.
"I was on the seventh floor and the light went off in the whole sector, and we evacuated. People were very anxious in the street ... We left barefoot."
Across the Pacific in Japan, a 7.3 magnitude tremor struck Kumamoto province early Saturday, killing at least 32 people, injuring about a thousand and causing widespread damage, in the second major quake to hit the island of Kyushu in just over 24 hours. The first, late on Thursday, killed nine.