Gabonese President Ali Bongo has been hospitalised in Riyadh, Saudi state media said, without giving more details.
Saudi Crown Prince Mohammed bin Salman visited Bongo in Riyadh's King Faisal hospital and "inquired after the health of the president", the official Saudi Press Agency said in a brief dispatch on Thursday.
Bongo, 59, was scheduled to appear Wednesday on a panel at the flagship Future Investment Initiative forum in Riyadh, but he was not seen during the discussion and organisers of the conference offered no explanation.
But in a separate dispatch, SPA said Bongo attended a speech by Prince Mohammed at the conference later Wednesday.
Gabon's presidency appeared to downplay the development, telling AFP it was "nothing serious" and that Bongo was tired.
Bongo took over as leader of the oil-rich equatorial African nation in 2009 on the death of his father Omar Bongo, who had ruled since 1967.
In 2012, Ali Bongo was re-elected by just a few thousand votes in controversial presidential polls.