Borussia Dortmund are aware of increasing transfer interest in defender Neven Subotic.
The Serbia international attracted enquiries from Manchester City and Chelsea over the summer, though insisted he was happy in Germany.
Now, German sources say Manchester United and Real Madrid have also made Dortmund aware of their interest.
There is speculation of a January move away for Subotic, though the US-raised defender insists he wants to at least see out this season in the Bundesliga.
