Belgian Tom Boonen stormed to a record-equalling third career victory in the Tour of Flanders while 2010 winner Fabian Cancellara fell and broke his collarbone.

The 31-year-old Omega Pharma-Quick Step rider outsprinted Italians Filippo Pozzato and Alessandro Ballan to become the fifth rider to take three wins in the 99 year-old event, Belgium's top one-day classic.

Two leading New Zealand riders completed the tour, with Hayden Roulston 21st on general classification and Tom Bauer 64th.

The winner of the prestigious Belgian E-3 Harelbeke and Ghent-Wevelgem classics last weekend and now the new leader of the UCI WorldTour rankings, Boonen has seemed all but unstoppable in 2012 after a quiet 2011.

The leading three formed a breakaway 17 kilometres from the finish on the third ascent of the short but very steep Oude Kwaremont climb, then Boonen beat the two Italians in a long final sprint.

"I was surprised as well as pleased to win, because I was not feeling at all good earlier on," Boonen, the winner of the Tour of Flanders in 2005 and 2006, told reporters.

"I was feeling so rough that in fact I knew I couldn't drop the other two before the finish and I'd have to gamble on a sprint."

"Fortunately if I was tired, so were the rest. It's been an amazing race with an amazing result."

Boonen's closest pursuer Pozzato said that a crash that saw leading favourite Cancellara abandon around the 200 km mark was a key moment.

"It made a big difference," Pozzato told reporters. "The other teams really increased the pace and things got a lot tougher."

"I thought Tom was not having a good day, he dropped back a bit on one of the final climbs and I thought that was a good sign. But he was just as strong as ever in the last sprint."

Cancellara's RadioShack team said the 2008 Olympic time trial champion had suffered a triple fracture of the right collarbone and would undergo surgery in Basel.

Boonen, a triple Paris-Roubaix winner, was cautious when asked whether he could equal compatriot Roger De Vlaeminck's record four victories in 'the Hell of the North' next Sunday.

"I've been racing all out for some time now and for now I just want to enjoy the feeling of taking three Flanders," Boonen said. "But I'll look forward to the challenge."

"Hopefully he'll be a bit tired," added Pozzato, "Otherwise we won't have that much of a chance against him."

- © Fairfax NZ News