The epicenter of both tremors was at a shallow depth of 35 kilometers, the US Geological Service said. Ecuador is still reeling from a deadly 7.8-magnitude quake that struck on April 16, 2016.
A 6.4 magnitude earthquake struck northern Ecuador on Sunday in the same area devastated by a powerful quake in mid-April, the US Geological Service (USGS) said.
Its epicentre was 41 kilometres (25.5 miles) south of the town of Propicia - located next to the quake-devastated coastal town of Esmeraldas - and 154 kilometres (96 miles) northwest of the capital Quito, the USGS said.
The quake, which struck at 9:11 pm (0211 GMT Monday), was preceded just minutes earlier by a 5.9 magnitude quake with an epicentre one kilometre away.
There were no immediate reports of casualties or damage.
Earthquake monitors in Ecuador had slightly different readings on the magnitude of the quakes.
The epicentre of both tremors was at a shallow depth of 35 kilometers, the USGS said.
Ecuador is still reeling from a deadly 7.8-magnitude quake that struck on April 16, killing some 700 people.
The quake flattened homes and buildings up and down a long stretch of Pacific coast, reducing picturesque resort towns to rubble.