Backed by Russian billionaire Dmitry Rybolovlev, Ligue 2 champions Monaco recently splashed out €70million on Porto pair Joao Moutinho and James Rodriguez.
Mandanda, Marseille's 28-year-old club captain, has been linked with Arsenal, Tottenham and Liverpool in the past and could command a fee of €15million.
In 2011, N'Koulou, 23, moved from Monaco to Marseille and club chairman Vincent Labrune is dismissive of reports linking him and particularly Mandanda with the big-spenders from the Principality.
"There was no concrete offer from Monaco to l'OM, and there was no concrete offer from Monaco to the player," Labrune said.
"Last summer lots of clubs tried to lure me with a fee, but one year later I am still waiting.
"There is no Mandanda case. Last summer we were in big financial trouble and we could have listened to propsitions, but now we are fine."