The move is set to pave way for Egyptian hitman Mohamed Zidan, who spent most of last season as a benchwarmer to Frei and Paraguay forward Nelson Haedo Valdez.

Frei scored over thirty goals for Dortmund since he joined the club from French Ligue 1 side Rennes in 2006.

The 30-year-old has 67 international caps and 39 goals for his country.

Dortmund are reportedly looking to replace Frei with Werder Bremen's Ivorian striker Boubacar Sanogo, who spent last season on loan at Hoffenheim.