RIO DE JANEIRO — President Jair Bolsonaro of Brazil was flown to São Paulo on Monday and hospitalized for treatment of a possible stomach obstruction after experiencing discomfort while on vacation in the southern state of Santa Catarina, his office and a hospital said.

He was admitted to Vila Nova Star hospital, where he was undergoing exams under the care of Dr. Antônio Luiz Macedo, the surgeon who treated Mr. Bolsonaro after he was stabbed in 2018 while campaigning for president. Mr. Bolsonaro is in stable condition, the hospital said, adding that five doctors were overseeing his care.

In a post on Twitter, Mr. Bolsonaro said he “started feeling poorly after lunch on Sunday.” After arriving at the hospital at 3 a.m., he wrote, he was administered a nasogastric tube, which can be used to drain fluid from the stomach of a patient with an intestinal obstruction. The president, who included a photo from the hospital in the tweet, said that more exams would be conducted to determine whether surgery was necessary.

He added that the symptoms were the same ones that led to a brief hospitalization in July and cited his stabbing in 2018 as the underlying cause of his health problems.

The injuries he sustained in that attack required at least four surgeries. The stabbing severely injured Mr. Bolsonaro’s intestines and led to a lengthy hospitalization that effectively knocked him off the campaign trail in the final stretch.

Mr. Bolsonaro nonetheless pulled off a decisive victory. The president has suggested — without evidence — that political rivals masterminded the attack.

A judge in 2019 found that the assailant was mentally ill and as such could not be convicted of a crime. The judge ordered that the assailant, Adélio Bispo de Oliveira, be held at a mental health ward in the prison system until public safety officials determined he no longer posed a threat. The president was last hospitalized in July after experiencing a bout of hiccups that lasted several days and caused stomach pain.

Dr. Macedo, who was on vacation in the Bahamas, was to fly to Brazil on Monday to see the president, and Mr. Bolsonaro said on Twitter that he would arrive at 3 p.m. The doctor told the news site UOL that it was too early to tell whether the president’s condition was serious. He said he could be experiencing an intestinal obstruction for something as common as not chewing his food properly.