Ecuador's strongest earthquake in decades killed at least 41 people and caused damage near the epicentre as well as in the largest city of Guayaquil.
RNZI reports President Rafael Correa declared a national emergency and urged the 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.
The government said the death toll would likely rise and damages were "serious", especially in the western coastal areas nearest to the quake's centre 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 20km and was felt all around the country.
Guayaquil Mayor Jaime Nebot, who was travelling in Spain, said on his Facebook page he would coordinate recovery operations from where he was.
Official details on the damage to Guayaquil, a frequent departure point for foreign tourists visiting the Galapagos islands made famous by Charles Darwin, were slow to emerge.
Social media pictures showed a collapsed bridge in the city 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.
"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," said Lorena Cazares, 36, a telecommunications worker in Quito.
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 centres.
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 one 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 epicentre, had been halted as a precaution.
"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.
The Ministry of Civil Defence said there was no threat of a tsunami reaching New Zealand as a result of the earthquake.