At least two victims have been identified, according to the newspaper.
An official with Ecuador’s navy told The Associated Press that the suspects tried to leave the scene aboard three boats, but were blocked by the coast guard. The official spoke on the condition of anonymity, because he wasn't authorized to talk about the case.
One boat was able to flee, while the occupants of the two other boats jumped into the water and disappeared into the mangroves. No suspects were arrested, the official said, adding that munition was found aboard the two abandoned boats.
Authorities have yet to publicly comment on the attack. It occurred less than 48 hours after the government placed El Oro province under a two-month state of emergency following a surge in violence.
President Daniel Noboa, who was re-elected in May, has pledged to tackle drug trafficking and violent crime.
The South American country of around 18 million people reported about 8,000 killings last year, with crime surging this year.