Ecuador's Congress voted overwhelmingly to lift presidential term limits from 2021, triggering violent demonstrations that saw police attacked with spears, clubs and home-made rockets.
Ecuador now joins fellow leftist-led Latin American nations Venezuela and Nicaragua in allowing multiple re-elections.
After nine hours of debate, and opposition protests in the streets of Quito and other cities, the legislature — dominated by supporters of President Rafael Correa — voted 100-8 in favor of the constitutional amendments.
While the legislature barred Correa from running for re-election in the 2017 national polls, he could become a candidate in 2021. The socialist leader has been in power since 2007.
Protests, sometimes violent, were held in the country's main cities, including Guayaquil, Ecuador's most populous city.
Protesters wanted lawmakers to refrain from voting on the proposal, or at least have it put to a popular vote — as will happen in Bolivia in February.
the capital Quito, Interior Minister Jose Serrano said that a "violent" group attacked police with spears, stones and clubs.
Outside Congress, a large crowd hurled stones, clubs and fired rockets at police, who took cover behind large shields.
Protesters, some wearing hoods, were seen charging riot police on horseback with spears.
"We're living in a dictatorship. This is a dictatorship because it's arrogant and authoritarian, it's a government that does what it wants with our resources," said one protester, Patricia Pinto, 43.
Protest organizers said that 20 people had been arrested, but police did not release arrest figures.
"Indefinite re-election is a mechanism that can provide moments of stability," but ultimately it "weakens democracy," political scientist Daniel Montalvo told AFP.