Rubin Kazan have made a £15.4m offer to Celtic for forward Odsonne Edouard, while Everton have also shown an interest in signing the striker.
The Russian club are proposing to pay the fee in three instalments over 12 months with the first payment around £8.5m followed by two blocks of approximately £3.4m.
Everton have sounded out a deal to bring the forward to Goodison Park, with manager Rafael Benitez also keen on Brighton's Neal Maupay - although the Toffees are in a position where they must sell to buy as the club remain hamstrung by Financial Fair Play rules.
Bordeaux are also willing to match Rubin Kazan's bid for the French striker.
In January, Sky Sports News reported Edouard would look to move to one of the top European leagues this summer with his Parkhead contract running out in June 2022.
Leicester also held talks over the in-demand striker in June with Brendan Rodgers a keen admirer of Edouard, having signed him as Celtic boss in 2017 on an initial loan deal from Toulouse before the club acquired him on a permanent deal for a club-record £9.3m from Paris Saint-Germain a year later.
Celtic boss Ange Postecoglou admitted earlier this month the possibility of Edouard leaving for free is a concern for the club.
Reports claim Edouard is prepared to let his contract expire, leaving him free to speak to other sides in January.
Postecoglou said: "I think you are in right in saying that is a club concern rather than my concern right now. No, [I'm] not concerned at all.
"If it means he stays here and contributes then so be it, but again that is stuff that I am not really spending too much time thinking about.
"I have been at pains to say that there are certain things that are out of my control that I'm just not going to waste time during this period anyway, where it is really hectic, thinking about it.
"My total focus is getting the team ready for these games, playing our football which is not easy and needs a lot of attention from me and the staff, and also working on bringing players in.
"I have left outgoings totally to other people, that's other people's concerns.
"You are probably right, there is a concern there around cashing him in, but those are probably questions for other people."
Celtic close in on Giakoumakis
Meanwhile, Celtic are close to agreeing personal terms with VVV-Venlo striker Georgios Giakoumakis.
It is understood a fee of around £2.5m has been agreed in principle between the clubs.
The Greece international was also speaking to Werder Bremen, who were priced out of a deal - and opted to sign Marvin Ducksch from Hanover 96 and Roger Assale from Dijon.
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