A double tragedy has rocked the famous Sydney to Hobart yacht race after two sailors died in separate incidents.

Authorities reported that a crew member aboard one entry into the race was struck by a boom just before midnight - fellow members attempted CPR but were unable to revive them.

Around two hours later disaster struck again as another sailor was also struck by a boom and died.

New South Wales police are yet to release the names of the race entrants.

A total of seven boats have now withdrawn from the race, including favourite Master Lock Comanche due to sail damage.

The vessel, which has claimed line honours four times and is the race record holder, was leading the race when her withdrawal was announced.

Australia correspondent Murray Olds told Tim Beveridge the two sailors were killed by booms about an hour apart in nearly identical circumstances. 

He says the booms came over in the wild conditions and hit the sailors - and both died.

LawConnect currently leads the race.

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