He was admitted to the army hospital in the capital city of Brasilia for testing in the early hours of Wednesday, according to Globo.
Mr Bolsonaro was said to be “feeling well” in an initial statement from the president’s office, but hours later an update said the surgeon who operated on the far-right politician after he was stabbed in the abdomen during the 2018 presidential campaign decided to transfer him to Sao Paulo, where he underwent additional tests.
His son Flavio said Thursday it was unlikely there would be a need for surgery.
The president’s office said in a statement that Mr Bolsonaro was doing better and that his clinical and laboratory results were “satisfactory”, but it gave no expected discharge date.
The statement, signed by the president’s doctors, did not mention surgery.
His hospitalisation occurs at a moment that pressure has been mounting. A congressional committee is investigating his administration’s handling of the coronavirus pandemic, with witnesses alleging corruption in the acquisition of Covid-19 vaccines, and recent polls have shown low approval ratings and indications that he risks losing next year’s election.
Mr Bolsonaro, who is Catholic and evangelical, posted on his official Twitter and Instagram accounts a photo of himself lying on a hospital bed, eyes closed, with several monitoring sensors stuck to his bare torso.
At the edge of the photo, a hand reaches out from an unseen person wearing what appears to be a black religious robe and a long chain with a gold cross.
The president’s 2018 stabbing caused intestinal damage and serious internal bleeding and the president has gone through several surgeries since, some unrelated to the attack.
In recent weeks, Mr Bolsonaro has appeared to struggle with speaking on various occasions and said that he suffers from recurring hiccups.
“I apologise to everyone who is listening to me, because I’ve been hiccuping for five days now,” Mr Bolsonaro said in an interview with Radio Guaiba on 7 July.
He suggested some medications prescribed after dental surgery might be the cause, adding: “I have the hiccups 24 hours a day.”
The far-right politician was placed in intensive care and lost 40 per cent of his blood when he was stabbed on the campaign trail in 2018 but went on to win the presidential election.
His attacker was acquitted in 2019 on the grounds that he was mentally ill.
Adelio Bispo de Oliveira pierced Mr Bolsonaro’s intestine, putting his life in danger, when he stabbed the leader with a knife in the streets of Juiz de Fora, north of Rio de Janeiro.
Additional reporting by agencies
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