Sydney - Eight-time line honours winner Wild Oats XI pulled out of the Sydney to Hobart on Saturday while American super-yacht Comanche was attempting repairs after fierce winds hit off Australia's east coast, officials said.
A 108-strong fleet set sail from Sydney Harbour earlier on Saturday, but by late evening 10 boats had retired, including one with a broken mast, the organising Cruising Yacht Club of Australia said.
"Wild Oats XI has retired from the race after reporting a torn mainsail," the club confirmed in a statement.
It said the Mark Richards skippered crew was returning to Sydney but no further details were available.
Early reports indicated the sail "tore in half when the yacht was hit by a 40 knot squall", the Wild Oats XI twitter feed stated.
Organisers said the crew of the Comanche, which had been leading the race after bolting out of Sydney Harbour, "will try to effect repairs to a rudder and continue racing".
The front half of the fleet in the gruelling 628 nautical mile (1 163km) race was enduring the brunt of the punishing weather as they sailed into "southerly buster" gale force winds, the CYCA added.
The navigator on one of the leading yachts, Ichi Ban's Will Oxley, had reported gusts of up to 43 knots while another boat, CEX Dolce, was returning to Sydney with a broken mast, it said.
Officials had warned of thunderstorms and gales late on Saturday as the fleet travelled down the east coast of Australia.
Storms are not unknown to the race, with six people dying, five boats sinking and 55 sailors rescued on a fatal night in 1998 when a deep depression exploded over the fleet in the treacherous Bass Strait.
It was an eventful beginning to the race, with three yachts retiring early after collisions just after the start, and another a short time later.
Among them was Ark323, one of two Chinese entries and one of 27 foreign boats in the race which draws spectators on land and in boats in Sydney on Boxing Day.
"Ark323, one of two Chinese entries, retired following a collision 300 metres after the start. All on board were safe," race organisers said in a statement.
Australian boat Cougar II retired at about the same time with damage to her starboard quarter while the British entry Lupa of London also pulled out with a damaged bow after a collision.
Another boat, M3, withdrew after shattering its forestay, her crew deciding that the harsh weather forecast ruled out a possible repair and rejoining of the race.
Line honours contender supermaxi Perpetual Loyal and St Jude were later retirements, both understood to have sustained rudder damage from the rough weather in the evening, while Koa withdrew with steering damage.
Last year's line honours winner Wild Oats XI had initially led in the moments after the starter's horn blew, but was overtaken by Perpetual Loyal before Comanche took the lead after unfurling her big spinnaker.
Wild Oats holds the race record of one day, 18 hours, 23 minutes and 12 seconds set in 2012 and her retirement and Comanche's rudder damage open up the race for line honours.
Rambler was in the lead late on Saturday, ahead of Comanche, Ragamuffin 100 and Maserati.
A brief update from Ragamuffin reported conditions as "wet and windy" as the leaders tracked down the New South Wales coast.
The winds are expected to ease on Sunday, and will be light off the coast of Tasmania as the boats head to Hobart's Constitution Dock, with the first boats not expected to cross the finish line until Monday.