Brazilian President Jair Bolsonaro, 66, may need emergency surgery after suffering persistent hiccups for 10 days, his office says.
He is being transferred to a hospital in São Paulo to undergo tests for an obstructed intestine. In a tweet, Mr Bolsonaro said he would be “back soon, God willing”.
There have been concerns about the far-right leader’s health since he was stabbed in the intestines while campaigning in 2018.
Mr Bolsonaro was seriously wounded in the attack and lost 40% of his blood. He has had several operations since the stabbing.
The president went to the military hospital in Brasilia early on Wednesday, and medics said then that he would be under observation for 24 to 48 hours.
But later the same day, the president’s office said Antonio Luiz Macedo, the surgeon who operated on Mr Bolsonaro in 2018, had recommended the president be transferred to São Paulo for additional tests and possible surgery.
Fabio Faria, Brazil’s communication’s manager, told reporters Mr Bolsonaro had been sedated in the morning ahead of being taken to São Paulo.
The president’s son Flavio told CNN Brasil that his father had undergone a procedure to remove liquid from his stomach as a precaution.
Flavio added that his father had had trouble speaking, but that if surgery were needed it should not be a serious procedure.
Mr Bolsonaro earlier tweeted a photo of himself lying in a hospital bed, fitted with sensors and cables, with someone who appears to be a priest standing by his bedside.
After two-and-a-half years of a controversial presidency, Mr Bolsonaro is under growing pressure over his handling of the Covid-19 pandemic.
At the beginning of the month, tens of thousands of people took to the streets to protest over allegations of corruption involving the purchase of vaccines.
The Brazilian leader has been heavily criticised for a lack of a national response to the crisis and his scepticism toward vaccines, lockdowns and mask-wearing requirements.
Last month, deaths with the virus in Brazil passed 500,000, the second-highest in the world after the US.
Mr Bolsonaro himself caught Covid-19 a year ago but has fully recovered.