The Senegalese international, who has hit 20 goals in 60 games for Les Licornes since joining from Swiss side Sion in 2017, had also been linked with Turkish side Fenerbahce and Amiens' Ligue 1 rivals Saint-Etienne - but neither club have made an offer, according to Footmercato, which also claims Rangers and the player's representatives have been in contact "for several days" with no movement.
L'Equipe claimed last month Rangers were prepared to pay £9 million for the 26-year-old, but only if Colombian striker Alfredo Morelos departed the club. Rangers are, at the time of writing, also finalising a £7 million deal for Liverpool winger Ryan Kent.
El Bufalo has remained at Ibrox and while reports suggest Rangers retain an interest in the striker, Celtic are also being linked with the former Maccabi Tel Aviv and Krasnodar man by Footmercato.
The Hoops have completed the signing of Greg Taylor from Kilmarnock while Manchester City's 18-year-old right-back Jeremie Frimpong and 19-year-old Manchester United centre-back Lee O'Connor have also been linked with the Parkhead side.