The quake lasted more than 20 seconds and caused panic in Quito, where residents evacuated buildings after it struck at 2.58pm on Tuesday (7.58 Wednesday NZT).
Watch: Strong Quake kills 367 in China
"I was talking on the phone with my daughter and suddenly the line went dead. I thought the house was falling down," Laura Flores, a resident of Quito's northern Carcelen district, said.
She added the quake had opened a crack in one wall of her house and caused several plates to fall and break.
The country's Geophysics Institute said the quake occurred at a depth of five kilometres and was followed by a forceful aftershock. It warned that more small aftershocks were possible.
Emergency services said the epicentre was near Mitad del Mundo, a tourist attraction at the equator where a monument is being built at the dividing line between the northern and southern hemispheres.
- AAP / AFP