Hughes admits he's following the former Schalke striker for several years.
He said: "He is a player who has been on my radar for quite some time now, in fact it was when he played for Hamburg I first saw him and took note of how good a player he was.
Hughes, who was speaking to the club, added: "He is a talented guy who has good pace, power and real presence too. I really believe the supporters will enjoy watching him play.
"We actually tried to bring him here a couple of windows ago, but for whatever reason we weren't able to get the deal done, but thankfully we have been able to do so this time, and I am delighted."