Australia claimed three gold medals on the fourth day of competition at Melbourne's Hisense Arena and leads the championships tally with five golds and a total of 12 medals. Britain is second with five golds and eight medals overall, ahead of Germany with two golds and a bronze. Four titles will be decided on the final day Sunday.

Hepburn, who qualified fastest earlier in the day, beat Bobridge by more than half a second.

New Zealand's Westley Gough spoiled the home riders' hopes of an all-Australian podium by beating Rohan Dennis for the bronze.

"We were all really keen to go 1-2-3 today, but unfortunately we didn't do it," Hepburn said. "But (Dennis) still had a great ride, he did two great times and I think he should be happy with himself." Frenchman Gregory Bauge won the men's sprint in contentious circumstances after Britain's Jason Kenny had his finals-leveling win overturned in the second heat.

After Bauge took a highly tactical first heat, Kenny made an early break in the second and held on to force a decider, but after several minutes of deliberation officials ruled Kenny crossed the sprint line and reversed the outcome prompting a chorus of boos from the crowd.

"It's just the way it is. The rules are the rules," Kenny said. "You can clearly see on the video that I came out of the red so you can't really argue with that." Chris Hoy won the bronze when he beat Australia's Shane Perkins in consecutive rides.

Kenny earlier improved his chances of claiming the sprint berth on the British Olympic squad after beating Hoy to reach the finals.

The world championships is the last Olympic qualifier before the London, and changes to the qualification process dictate that each nation can only have one representative in the sprint events at the games.

"There was no gold medal, but I guess it gave (the selectors) something to think about and he did a really good ride," Hoy said. "Whoever gets to ride for (Britain) at the Olympics in the sprint will do a good job I'm sure." Kenny will be hoping he's done enough to ensure that rider is him.

"I definitely feel I put a good showing in here today, but it's out of my hands now," he said.

Anna Meares of Australia won a hard-fought sprint in the final meters to defend her women's keirin title.

Meares reeled in the early breakaways to surge to the front of the pack in the final meters. Ekaterina Gnidenko of Russia was second with Germany's Kristina Vogel third.

Earlier, Victoria Pendleton was eliminated from the keirin a day after claiming the sprint title.

Pendleton scraped through early qualifying and advanced via the repechage, only to finish sixth and last in her second-round heat.

The Olympic champion beat defending world champion Meares in the sprint semifinals Friday night after crashing in one heat and profiting from an official intervention in another.

"It doesn't make up for last night, it makes today special," Meares said.

"I'm really proud of the way I was able to pick myself up after the disappointment of last night," she said. "There's no better way to make you feel better than a win." Cameron Meyer gave Australia its third gold of the night when he took a lap with one lap remaining and held off Britain's Ben Swift in the final sprint to win the men's point race.

Swift took second place ahead of Kenny De Ketele of Belgium in third.

Laura Trott of Britain claimed her second winner's rainbow jersey when she won the final event of the multidiscipline omnium.

Trott — a member of Britain's title-winning team pursuit squad on Thursday — held off Annette Edmonson to win the omnium individual time trial and seal the six-discipline event by three points ahead of the Australian. Sarah Hammer of the United States took the bronze.

"I didn't expect to win and I thought maybe I could pick up a medal," Trott said. "But to win, I mean, what more can I ask for?" The omnium makes its debut as an Olympic medal event at the London Games.