His four goals in the Champions League rout of Real Madrid and expiring contract make striker Robert Lewandowski a hot target for Europe's top clubs but Borussia Dortmund now faces a fight to keep its Poland star.

His record haul against Real at Signal Iduna Park in Wednesday's 4-1 first-leg win made him the first player to score four goals in a Champions League semifinal and left Dortmund on the verge of its first Euro final since 1997.

The 24-year-old's Dortmund deal expires in June 2014 and he has already said he will not be signing an extension, having joined Borussia in 2010, but his advisor, Maik Barthel, has said Lewandowski will be gone by the close season.

"We are in agreement with a club and have the right to change this summer," Barthel told Sport Bild online. "There is a very interesting offer for Robert."