BEIJING, Aug 13, 2008 (AFP) - Michael Phelps set a new Olympic gold standard Wednesday, winning the 10th and 11th titles of his Games career and sparking an explosion of world records at the Water Cube.

Phelps swam into history with two triumphs an hour apart, lowering his own world record in the 200m butterfly then leading the United States to a record-shattering victory in the 4x200m freestyle relay - two of six world records in a stunning display of prowess in the pool.

All four finals produced world records, while the men's 100m freestyle world mark toppled twice in a matter of minutes in the semi-finals.

"I'm at a loss for words right now," Phelps said. "I just keep saying to myself 'greatest Olympian of all time' over and over.

"It hasn't sunk in yet, but it's a great thing to hear people say it."

In the butterfly, Phelps shaved six-hundredths of a second off his own world mark with a time of 1:52.03.

Not long after stepping off the medal podium he was back on the blocks, leading a US team that also included Ryan Lochte, Ricky Berens and Peter Vanderkaay to a time of 6:58.56 - destroying the previous 4x200m free world mark of 7:03.24.

Russia were a distant second in a European record of 7:03.70, and Australia were third in 7:04.98.

"He's just a normal person, although maybe from a different planet ... a planet from a different galaxy," said Russian relay swimmer Alexander Sukhorukov.

With five golds and five world records Phelps continued his progress toward another piece of Olympic history.

If he can win all eight of his events, he will surpass the record of seven gold medals at one Games set by US swimmer Spitz at Munich in 1972.

Laszlo Cseh of Hungary was second and Japan's Takeshi Matsuda third in the 200m fly.

Phelps's victory wasn't the majestic display of his 200m freestyle triumph on Tuesday, but he said there was a reason for that.

"My goggles were filling up with water during the race, and I had trouble seeing the wall," he said. "Given the circumstances it's not too bad."

"Just think how fast that would have been," gushed US men's head coach Eddie Reese.

Later Wednesday, Phelps cruised to the sixth-fastest time in the heats of the 200m individual medley, in which his two main rivals, teammate Ryan Lochte and Cseh, topped the times heading into the semi-finals.

"I'm just trying to get through everything, it's a lot of racing and it's not easy," said Phelps, who must swim 17 times in nine days. "I am trying to take one race at a time."

But Phelps, who also has the 100m butterfly and 4x100m medley relay remaining, spoke like a man in sight of the finish line.

"The end is close, I love it," he said, although he added in what sounded almost like a warning to himself that he couldn't afford to be complacent.

"I am not unbeatable, no one is unbeatable," he said.

Federica Pellegrini, 20, became Italy's first woman swimming gold medallist in the 200m freestyle.

The silver medallist from Athens sliced 0.63sec off the mark she set in the heats on Monday with a time of 1:54.82.

Slovenia's Sara Isakovic was second in 1:54.97 - also under the previous world record - capturing the first Olympic swimming medal for her country.

China's Pang Jiaying snagged the bronze in an Asian record of 1:55.05 - also under the previous world mark.

Australian Stephanie Rice lowered her own world record with a time of 2:08.45 in the women's 200m individual medley - completing a medley double that opened with a world-record win in the 400m medley.

Zimbabwe's Kirsty Coventry claimed her third silver of the Games in 2:08.59 - also under Rice's previous world record of 2:08.92.

American Natalie Coughlin (2:10.34) added the medley bronze to her 100m backstroke gold and relay silver.

Australian Eamon Sullivan emerged with the men's 100m free world record in a tit-for-tat exchange with France's Alain Bernard.

Bernard, swimming in the first semi-final, clocked 47.20 to better the record of 47.24 Sullivan had set in the lead-off swim of Monday's 4x100m free relay.

Minutes later Sullivan sliced a further 0.15sec off Bernard's just set record to reduce the world mark to an incredible 47.05 seconds.

Dutch star Pieter van den Hoogenband, who booked his place in a fourth straight 100m free final with the third-fastest time of 47.68, said he didn't see any chance of becoming the first man to win the same Olympic swimming title three times in a row.