It has been reported by the Belgian news outlet that Ajer is set to join Leicester in the Premier League and reunite with his former Celtic manager Brendan Rodgers.
90min reported only last week that Leicester are leading the race for the 22-year-old Norway international central defender.
Le Soir has claimed that Celtic have identified Waasland-Beveren centre-back Vukotic, 24, as a potential replacement for Ajer.
According to WhoScored, Vukotic made 26 starts and one substitute appearance in the league for Waasland-Beveren this season, scoring two goals in the process.
Good signing for Celtic?
Ajer has developed into a very good centre-back who can also operate as a defensive midfielder, and it would be a blow for Celtic if they were to lose the 22-year-old this summer.
While many will have doubts over Vukotic given that he would be coming from the Belgian domestic league, Celtic have had successes in the past of signing players from such leagues.