LONDON, April 24 (Xinhua) -- World number one Ronnie O'Sullivan came out the last to reach the quarter-finals of the world snooker championships after fighting back from behind to beat qualifier Ryan Day on Monday.

    Trailing 9-7 at the start of the final session, O'Sullivan managed to take advantage of some costly errors from Day to win six out of seven frames and seal victory.

    The Briton, seeking for his third world title, will take another twice former champion Mark Williams in the last eight.

    Ireland's Ken Doherty beat Matthew Stevens 13-8 to set up a quarter-final meeting with Hong Kong qualifier Marco Fu, while Peter Ebdon eased past David Gray 13-2 to date with defending champion Shaun Murphy.

    Scotland's Graeme Dott will face Australian qualifier Neil Robertson after completing a 13-9 win over Nigel Bond. Enditem