He arrived at Vila Nova Star Hospital Saturday night accompanied by his wife Michelle and his son Carlos.

It is his fourth operation since he was stabbed a year ago during the presidential campaign, with the latest surgery to correct a problem resulting from the previous procedures.

"The president has already gone through three large surgeries, including the last one, for abdominal reconstruction, and the region was quite weakened by invasive actions," his surgeon Antonio Luiz Macedo told the G1 news portal.

"It is a simple to moderate level surgery," he said. "No complications are expected."

The surgery forced the right-wing president to miss a summit of leaders from seven Amazon nations in Colombia to agree measures to protect the world's biggest rainforest.

He has been widely criticized over policies that favor deforestation and a delayed reaction to the wildfires that have devastated swathes of the Amazon.

Bolsonaro was stabbed in September, 2018 during a campaign rally in the state of Minas Gerais.

Attacker Adelio Bispo de Oliveira, 41, was arrested at the scene and said he acted alone.

De Oliveira, who medical authorities said suffers from mental problems, was ordered detained indefinitely in the psychiatric unit of a maximum security prison.