World heavyweight champion Wladimir Klitschko says Australia's Alex Leapai is "a real-life Rocky Balboa" who will be trying to take his head off in their April 27 title fight.

"Leapai is the underdog fighting an experienced champion," Klitschko said. "I can compare him to Rocky."

Leapai, who was born in Samoa, has a record of 30-4-3, with 24 KOs.

"There is pure violence in the way he fights, and he is going to do anything and everything to try to win," said the champion. "He is physically so strong that he doesn't need technique or strategy; pure violence is what we will see in the ring. For that reason, this will be an interesting fight to watch."

Klitschko (61-3, 51 KOs), undefeated over the past 10 years, will defend his WBC, WBO, IBF and IBO titles against the Brisbane father of six in Oberhausen, Germany. It will mark the first time in 106 years that an Australian has fought for the unified world heavyweight title.

Klitschko, who turned 38 last month, has proclaimed this the most important fight of his career, given that he needs to boost the morale of his native Ukraine, which is locked in a tense standoff with Russia.

"I know that Leapai is highly motivated and says he will knock me out in two or three rounds," said Klitschko. "If I lose my focus, I will lose the fight."

- Associated Press