By Agence France-Presse
The South American nation is still recovering from a devastating 7.8-magnitude quake that killed 673 people in April and left some 6,000 injured.
That quake flattened homes and buildings up and down a long stretch of Ecuador's northwestern Pacific coast, reducing picturesque resort towns to rubble. Hardest hit was the city and province of Esmeraldas.
"5 quakes over magnitude 4 in Esmeraldas," President Rafael Correa wrote early Monday on his Twitter account.
He added: "zones without electricity. Damage is being evaluated. Classes suspended in the province. Have courage!"
The strongest early Monday quake was centreed near the tourist resort of Atacames, in Esmeralda province, and struck at 0700 GMT.
Ecuador's Geophysical Institute initially said the quake was of magnitude 5.9, but later downgraded it to 5.8.
The US Geological Survey, which monitors earthquakes worldwide, said the quake was of magnitude 5.4.
The Geophysical Institute did not issue a tsunami alert, but warned that earthquake aftershocks could be expected.
Ecuador's national emergency service said that no damage was reported to the country's largest oil refinery, which is located in Esmeraldas province.