YORK, BRITAIN, Dec. 5 (Xinhua) -- Stephen Maguire upset world champion Mark Williams 6-5 in the last 16 of the UK Snooker Championship here on Wednesday.

Six-time winner Ronnie O'Sullivan also reached the quarterfinals by crushing Jack Lisowski 6-1.

Williams pulled ahead 4-0 but Maguire created a miracle and will next take on either Mark Allen or Neil Robertson.

Maguire, 37, fought back from behind to make runs of 122, 120, 109 and 97 to go 5-4 ahead. But leading by 20 points, he missed the final yellow and saw Williams cleare for 5-5.

Williams, who won the event twice, also wasted an early lead to let Maguire make 63 to clinch the result.

"I've never made a comeback like that," Maguire said. "For the first four frames I couldn't have been any worse. "

"It's a big scalp for me because I haven't been challenging the top boys so to beat the World Champion when he has been playing well - it doesn't get better than that."

O'Sullivan, celebrating his 43rd birthday on Wednesday and bidding for a record seventh title, took just 87 minutes to beat Lisowski. He now meets Martin O'Donnell or Ding Junhui. Enditem