The Turkish club's president, Baskan Aziz Yldirim, claims to have made a £5m offer for the Aussie, but Leeds confirmed they were unaware of any such bid.
"Viduka is a player we are following with a lot of conviction because he's the man who can help us to fill the gap with Besiktas, who are the strongest team in the league right now," said Yldirim.
"We're very close to him. We offered Leeds more than seven million euros. We expect the Australian to sign soon."
Leeds insist they have received no bid for Viduka, who is currently in Australia on indefinite compassionate leave, at the bedside of his ill father Joe.