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 has vowed to 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 adviser, Maik Barthel, has said Lewandowski will leave in June.

"We are in agreement with a club and have the right to change this summer," Barthel told Sport Bild.

"There is a very interesting offer for Robert, which corresponds to the obligations imposed by BVB in full and satisfies Robert's demands.

"BVB has assured us that Robert can change clubs at the end of the season, under these conditions.

"We will adhere to the agreement, now the clubs must provide clarity."

After Tuesday's announcement that Germany star Mario Goetze will join rival Bayern Munich in July, Dortmund is especially eager to keep "Lewo" and halt the dismantling of the team which won the Bundesliga the past two seasons.

Goetze has actioned a clause allowing him to join Bayern for a reported 37 million euros ($48.2 million) but Lewandowski's contract has no such condition, amid reports he is also set to head to Munich.

Lewandowski's manager, Cezary Kucharski, has told Polish television that the forward will soon "play at a bigger club", but Dortmund Chief Executive Hans-Joachim Watzke denied there was any deal to let the Poland star go at the end of the season.

"No, that's not true," Watzke told German sports news agency SID, an AFP subsidiary, with the final year of Lewandowski's contract reportedly worth 20 million euros.

"We will discuss everything with Robert."

Watzke has told German daily Bild he made Lewandowski a new offer last week.

"It is true that we have talked about new possibilities. It would be negligent if we did not try to continue to try to keep probably the best striker in Europe," said the Dortmund boss.

"If Robert really has an offer from a Bundesliga club, then I would expect them to talk to us, not only the player.

"To this day, we have received no offer. He has a contract with us until 2014 with no exit clause.

"Our explicit desire is that he stays and plays for us until 2014 at the least."

Lewandowski himself remained tight-lipped on the matter.

"We still have a few Bundesliga games left and hopefully two in the Champions League," he said. "That is the most important thing. For anything else we have to wait. I won't comment further."

In the event of his departure, Dortmund will have its work cut out to find a replacement who can match the 34 goals he has scored this term.

The haul includes 23 in this season's Bundesliga, where the Poland star has scored in each of his past 12 league games, setting a new club record, and he now has 10 in the Champions League.

Lewandowski's quartet betters both Ivica Olic's hat-trick in Bayern's 2010 Champions League semifinal win at Lyon in 2010 and Alessandro Del Perio's triple for Juventus in 1998.

He finished one short of Lionel Messi's Champions League record of five in a single match, against Leverkusen in 2012, while he matched Bayern's Mario Gomez four goals, in last season's 7-0 rout of Basel in the last 16.