Police said the 38-year-old Intriago, who was re-elected as mayor of Manta in February, had been inspecting public works in the city at the time of the attack.

Regional police commander Edwin Noguera told reporters a gunman got out of a stolen truck and opened fire on Intriago, hitting him and a woman described as a "collateral victim." Both died of their injuries.

Security officials with the mayor returned fire and wounded the driver of the vehicle, who is now in police custody while receiving medical attention in hospital. Noguera said the man was a Venezuelan national without a prior criminal record.

The suspected shooter escaped, Noguera said.

Police said officers had found a grenade in the truck and a gun which was likely used in the attack.

It was not immediately clear why the mayor had been attacked, though police said that he had reported receiving threats to authorities, without providing more details.

Ecuador has faced an increase in violent crime that the government says is driven by power struggles between criminal gangs over the drug trafficking trade.

Manta, a city of well over 200,000 people, has been prey to such gangs, while widespread common crime fed by economic and social problems is adding to the country's security woes.

President Guillermo Lasso expressed his sorrow over Intriago's "assassination" in a statement on Twitter and said he had ordered authorities to bring the killers to justice.

Former President Rafael Correa expressed his shock, saying on Twitter: "I can't believe this has happened."

In May, gunmen targeted the mayor of the city of Duran. He emerged unscathed from the attack but a policeman was killed and several other people were wounded, media reported.

Intriago belonged to a local political party in Manta.

Earlier, authorities said six people were killed at the weekend and 11 more injured in the latest outbreak of gang-fueled violence roiling Ecuador's prisons.