Ronnie O'Sullivan (L) of England shakes hands with Mark Allen of Northern Ireland after the match in the 2011 Snooker Masters held at the Wembley Arena in London, Britain, Jan 11, 2011. [Photo/Xinhua]

LONDON - Three-time world champion Ronnie O'Sullivan suffered first round exit at the Snooker Masters as he was beaten by Mark Allen 6-4 at Wembley Arena on Tuesday.

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Neither player was at their best but O'Sullivan made more mistakes during the match. Although the 35-year-old O'Sullivan managed to level it at 4-4 by winning two straight frames after following behind at 2-4, his below-par performance finally ended his trip at 4-6.

"From 4-2 to 4-4 Ronnie put me under pressure but overall he wasn't at his best," said the 24-year-old Allen, who advanced into the quarterfinals of the Masters for the third consecutive year.

As the 12th seed, Allen is going to meet the winner between Neil Robertson and Stephen Hendry.

After Allen's victory, veteran Marco Fu from Chinese Hong Kong knocked out Stephen Maguire 6-4.