Kirsan Ilyumzhinov has known Gadhafi for years. His visit to Tripoli this summer was the last time the Libyan leader was seen in public after NATO airstrikes began.
The two of them were filmed playing chess together on June 12.
Ilyumzhinov told The Associated Press that Gadhafi called him around 6 p.m. Moscow time (1400 GMT, 10 a.m. EDT) Tuesday and said he was not planning to leave Libya and "we will fight."
Gaddafi's whereabouts have been of intense interest as rebels have claimed control over much of Tripoli and fierce fighting erupted around his main military compound.
Ilyumzhinov said Gadhafi's voice was calm. He spoke in Arabic and his son Mohammed, Libya's Olympic chief, translated his words into English.
The phone call was brief, not much more than a minute, and Gadhafi promised to call him later, the Russian said.
The two men have known each other since at least 2004, when the chess federation, known by its French acronym, FIDE, held its world championship in Tripoli.
Ilyumzhinov, a wealthy businessman, had been the leader of the predominantly Buddhist province Kalmykia from 1993 until he stepped down last October. He is known for eccentric behavior and once claimed to have been abducted by aliens
