According to he German newspaper Bild, Gundogan is looking to leave Dortmund this summer after turning down a contract extension.
The Germany international has 15 months remaining on his current contract meaning Dortmund may be forced to sell him or risk losing him on a free transfer.
Dortmund also rejected an approach from Manchester United earlier on in the season according to the German newspaper Express.
The 25-year-old has also been linked with a move to Liverpool. The Red’s boss Jurgen Klopp does of course know Gundogan well from his time managing the Dortmund prior to taking charge of Liverpool
Dortmund sit in second place in the Bundesliga with 48 points in 21 games. The Bundesliga giants take on Porto in the UEFA Champions league this week.
Gundogan has six assists and three goals in 32 appearances for Liverpool this season.