The institute said the quake was felt “nationwide” by residents.
The quake struck at 17.3 (22:30 GMT) and was centered 13 km from the village of Simon Bolivar, near the port of Guayaquil.
Ecuadorian President Guillermo Laso called on residents to “calm down”. He tweeted that the authorities were “evaluating the potential damage in thearea”.
“At first I thought it was wind and suddenly I felt everything was moving,” Maria Eugenia Rosero, a teacher, told AFP. in pension living in the north of Guayaquil. He added that the earthquake “was short but strong”.
The city council, which has a population of around three million, indicated that a city house in demolition had collapsed and some buildings had suffered minor damage.
Residents of the area got out in square to shelter from possible landslides.
Ecuador is located on the marine plates of Nazca and South America, which leads to frequent earthquakes.