MELBOURNE -- Unseeded Frenchman Jo-Wilfried Tsonga gatecrashed the Australian Open semi-finals Tuesday in just his fifth Grand Slam with a straight sets victory over Mikhail Youzhny.

The athletic Tsonga, ranked 38, claimed his third seeded opponent of the tournament with a 7-5, 6-0, 7-6 (8/6) win in two hours 17 minutes.

It set up an intriguing clash with second seeded Spaniard Rafael Nadal on Thursday for a place in Sunday's final.

Triple French Open champion Nadal reached his first Australian Open semi-final with a commanding 7-5, 6-3, 6-1 victory over Finland's Jarkko Nieminen.

"I played just unbelievable, it's just amazing, I don't know what to say... incredible," an elated Tsonga said after his victory.

"I tried to be relaxed because it's a big event for me and it was difficult to stay calm, it worked and I'm very happy about that."

Of his semi-final assignment against Nadal, he said: "It's going to be difficult. I'm going to have to run again and again, so I will do my best and I hope to play like today."

Tsonga has now knocked out ninth seed Andy Murray, world number eight Richard Gasquet and 14th seed Youzhny to reach the last four.

The 22-year-old, nicknamed Muhammad Ali for his likeness to the boxing legend, has now won four of his last five matches against top 15 players.

His ranking is projected to be inside the top 30 when the new ATP rankings are released next Monday, and he becomes the seventh unseeded Frenchman to play in a Grand Slam semi, the last being Cedric Pioline at the 1999 US Open.

Tsonga, playing full of confidence, is looming as the unheralded player of the season-opening major tournament, much like Marcos Baghdatis and Fernando Gonzalez, who lost to Roger Federer in the last two finals.

Tsonga's victory ended Youzhny's nine-match winning streak after his victory over Nadal in the Chennai ATP tournament in India on the way to the Australian Open.

The Russian was bidding to reach his second Grand Slam semi-final after losing to Andy Roddick at the 2006 US Open.

Tsonga had a set point in the 10th game but Youzhny rescued it. He wasn't so lucky in his next service game when the Frenchman played a majestic backhand crosscourt to take the set and jumped with joy back to his chair.

Youzhny sought treatment for foot blisters before he suffered a triple break as Tsonga surged to the second set in just 29 minutes.

The Frenchman dominated the points 26 to nine while Youzhny looked only a shadow of the player who ousted fourth seed Nikolay Davydenko in the fourth round.

Tsonga reeled off nine games on the trot from the last game of the opening set to the first game of the third set to rattle the Russian.

But Youzhny dug in during the third set and made more of a fight, holding off a break point in the sixth.

Tsonga saved more excitement in the final set tiebreaker, fighting off a set point at 5-6 and then bringing up match point with a ripping serve before taking the match when a Youzhny volley went over the baseline.