A strong 6.3 magnitude earthquake struck northern Ecuador late Sunday in the same area devastated by a powerful and deadly quake in mid-April, the US Geological Survey said.

Its epicenter was 42 kilometers (26 miles) south of the town of Propicia -- located next to the quake-devastated coastal town of Esmeraldas -- and 153 kilometers northwest of the capital Quito, the USGS said, revising earlier figures.

The quake, which struck at 9:11 pm (0211 GMT Monday), was preceded just minutes earlier by a 5.8 magnitude quake with an epicenter at the same spot.

The USGS revised slightly downward its initial estimate of the strength of both quakes. Earthquake monitors in Ecuador had similar readings.

Ecuador is still reeling from a deadly 7.8-magnitude quake that struck on April 16.

At least 673 people were killed in the April 16 quake, and more than 6,000 injured, according to official figures.

The quake flattened homes and buildings up and down a long stretch of Pacific coast, reducing picturesque resort towns to rubble.

Ecuadoran authorities urged calm late Sunday, and said they should expect more tremors, all aftershocks of the April earthquake.

President Rafael Correa said there would be no classes on Monday in the quake-affected area so that school buildings could be inspected for structural safety.

At least one person was injured in the quake, Security Minister Cesar Navas said, adding that the Esmeraldas oil refinery and the province's port reported no damage.

"We're going to have this type of earthquakes for a long time," said Alexandra Alvarado, head of the Geophysical Institute, in an interview with the Ecuavisa network.

Blackouts were reported in several area cities, and landslides were reported on mountainous roads.

"Another very strong one. Again the nightmare," Santo Domingo resident Marcela Arellano told AFP.

She said that in the streets "children were crying, and everyone was scared."

According to the Geophysical Institute, there have been 2,134 aftershocks since the April 16 earthquake. The strongest aftershocks came in May and was of magnitude 6.8.

The late Sunday earthquake was also felt in parts of Colombia, officials in the neighboring country said.

pld-ch/pdw

APRIL