Melbourne, Jan 22 : Rafael Nadal saw off another challenge to his title defence at the Australian Open Friday while US Open champion Kim Clijsters was handed a shock third-round loss.

Second seed Nadal defeated German Philipp Kohlschreiber 6-4, 6-2, 2-6, 7-5 with the straightforward win propelling the Spaniard into the fourth round and a 5-0 mark over his opponent after three and a half hours.

"It was a very close match," said Nadal. "At five-all in the fourth set, anything can happen.

"He had a few forehand errors which helped me. I'm happy to be in the fourth round."

Other men's seeds also came through, with US Open winner Juan Del Potro of Argentina beating Florian Mayer of Germany 6-3, 0-6, 6-4, 7-5.

Number five Andy Murray dispatched Frenchman Florent Serra 7-5, 6-1, 6-4 to reach the fourth round for the third time in four years

But the Briton chilled the crowd as he grasped his back in pain after being wrong-footed on a return, calling for a towel but playing on to victory.

"Sometimes it happens on these courts, they're just really sticky. But it was fine." he said.

Seventh seed Andy Roddick rained down 29 aces to put out defeating Spain's Feliciano Lopez 6-7 (4-7), 6-4, 6-4, 7-6 (7-3), while 2007 finalist Fernando Gonzalez required five set to hold off Evgeny Korolev 6-7 (5-7), 6-3, 1-6, 6-3, 6-4.

"It was a long match; I'm just relieved to be through," Roddick said after reaching the fourth round.

The four-time semi-finalist improved to 6-0 over Lopez, winning with 21 unforced errors.

The collapse of US Open winner Clijsters provided all the drama needed on Day 5.

The mother of one who reversed her retirement last year and went on to claim the US Open in only her third event back on the WTA, literally fell apart in a 0-6, 1-6 loss to Russian Nadia Petrova.

"The way that I played today, I was completely off," said the Belgian, a two-time Grand Slam champion. I didn't feel the ball at all.

"On the other hand she was good. But I made all the mistakes and she didn't really have to do much.

"She served really well and was aggressive in the rallies, but that's because I let her play into the courts. Just because I wasn't feeling the ball well - it sucks."

Petrova won the first nine games before the Belgian 15th seed registered on the scoreboard, with the Russian schooling the 27-year-old in a quick-fire 52 minutes.

Second seed Dinara Safina moved ahead 6-1, 6-2 over Britain's Elena Baltacha.

Alona Bondarenko of the Ukraine sent eighth seed Jelena Jankovic to her quickest Melbourne Park loss since 2006 with a 6-2, 6-3 defeat.

Belgian comeback queen Justine Henin looked like she had hit the wall early in her struggle with Russian Alisa Kleybanova before rallying for a 3-6, 6-4, 6-2 win in just under two and a half hours.

The former number one and seven-time Grand Slam champion proved her pedigree in the comeback, rallying from a set and 3-1 down.

"I kind of survived a little bit today," Henin said. "It's always good to win this kind of match because I came back from nowhere.

"I'm very happy that I'm still in the tournament, that I have another chance to get better in the next round."

Henin advanced into a match against compatriot Yanina Wickmayer as the US Open semi-finalist also had her share of troubles in a win over Sara Errani 6-1, 6-7 (4-7), 6-3.

Wickmayer was stretched out on her stomach and given pain tablets late in the second set for treatment of back pain in a contest in which she won the opening set easily but had to battle to ensure final victory.(DPA)