Liberia's new President Joseph Boakai failed to reach the end of his speech and had to be helped away from the podium during his swearing-in ceremony.
Mr Boakai, 79, had been speaking for around 30 minutes at his inauguration ceremony when it became clear that he was having difficulty continuing.
He failed twice to carry on speaking, and the ceremony was adjourned.
Some reports suggested that he suffered from heat exhaustion as the temperature reached more than 30C.
Video footage showed a man fanning papers near Mr Boakai's face, before he was taken away.
By then, Mr Boakai had already been sworn in as Liberia's oldest-ever president at the ceremony held at the Capitol Building, the seat of parliament in the capital, Monrovia.
After he was taken away, new Vice-President Jeremiah Koung spoke to guests and escorted them to the presidential dinner.
Mr Boakai narrowly defeated the outgoing president, former football star George Weah, in a run-off election in November.
Concern about Mr Boakai's health was a major issue during the election campaign, but he told the BBC that he was in good health and "age should be a blessing to this country".
Before he was forced to cut short his speech, Mr Boakai said: "Elections are over, partisanship must give [way] to the forward march of Liberia.
"I come to rekindle our hopes," the new president said, adding that dignity in public service and respecting the rule of law must be restored.
Mr Boakai was vice-president in Nobel Peace Prize-winner Ellen Johnson Sirleaf's government until 2018, and contested the presidency under the banner of the United Party (UP).
He defeated Mr Weah by just over 20,000 votes in a run-off election in November.
Mr Boakai also ran for the presidency in 2017, but lost to Mr Weah, who became Liberia's young-ever elected president.
BBC