Moscow said the media reports were "the height of fakery".
Russia has denied media reports that Foreign Minister Sergei Lavrov was taken to hospital at the Group of 20 summit in Bali.
Lavrov reportedly suffered a health problem following his arrival for the summit, Indonesian authorities said on Monday.
Three Indonesian government and medical officials told The Associated Press that the Russian diplomat was being treated on the resort island.
Two of the people said Lavrov was being treated for a heart condition.
All declined to be identified as they were not authorised to discuss the matter publicly.
Bali Governor I Wayan Koster said Lavrov later left hospital in good health. It was a "check-up" and he was "immediately returned", added Koster.
The officials said he was taken to Sanglah Hospital in the provincial capital, Denpasar. The hospital did not immediately comment.
Russian foreign ministry spokeswoman Maria Zakharova has denied the report as the "height of fakery".
"Sergei Viktrovich [Lavrov] and I are reading the news wires and cannot believe our eyes," Zakharova said on Monday.
Officials at the Russian Embassy could not immediately be reached for further comment.
Lavrov is the highest-ranking Russian official attending the G-20 summit which begins Tuesday. He had previously attended the ASEAN Australia-New Zealand Trade Area summit in the Cambodian capital Phnom Penh on Sunday, before flying to Bali.