Leicester are said to be the team keenest on securing the Norwegian’s signature but Everton, Manchester United, Wolves, AC Milan, Borussia Dortmund and Paris Saint-Germain are also believed to be tracking the defender.
Reports last month suggested that Ajer could fetch as much as £25m, with the 22-year-old’s agent having stated in March that the player could leave Celtic Park this summer.
Manager Neil Lennon quickly dismissed those claims by saying that the Hoops are under no pressure to sell the Norweigan international with the centre-half still having two years to run on his contract.
However, with the interest in Ajer growing, the Scottish champions may find it difficult to keep hold of him. The number of teams reportedly keen on snapping him up will, though, mean that they can demand a high transfer fee for the player.