Borussia Dortmund have urged Bayern Munich to make it clear whether they have any interest in striker Robert Lewandowski.

The Polish international has been the subject of much speculation in the German newspapers, with reports suggesting that a deal has already been struck between the two teams.

Both sides have denied reports and Dortmund general manager Hans-Joachim Watzke has called for Bayern to show their hand.

"The whole issue is really getting on my nerves," he said. "There are two scenarios.

"The first is that Bayern have no interest in Robert, in which case it's all a load of rubbish. The other scenario is that they are interested and then they have got to lift their cover and come to us with an enquiry.

"When they do that, they will get an answer. Maybe that would even surprise them. Bayern are usually correct and if they have interest in a player, they will make contact."

Bayern are currently 15 points ahead of Dortmund at the top of the Bundesliga and the two rivals will play each other in the cup later this month.