The 147 is the third this year and 59th in professional snooker

The break took just over eight minutes and was one of five century breaks from the provisional world number two.

He will be joined in the quarters by Peter Ebdon, who secured a 5-0 whitewash of Steve Davis in Belfast.

And home hope Gerard Greene beat Ken Doherty 5-1 and next faces fellow Northern Irishman Mark Allen, who beat Welshman Ryan Day 5-3.

Neil Robertson will also be in the last eight after he dismissed Ian McCullough 5-0.

The Australian will now face Stephen McGuire, while O'Sullivan must overcome Fergal O'Brien if he is to reach the semi-finals.

But O'Sullivan insists he is not happy with his form at the �200,500 event, despite breaks of 108, 122, 107, 147 and 129.

"I got lucky because Ali made it easy for me because he missed a lot of balls," he said. "I can't face practising at the moment because I'm playing rubbish.

"It's nice to get 147s, though, it's a good feeling."

It was the seventh maximum of O'Sullivan's career.

606: DEBATE Who do you think will come out on top in Belfast? Saj C

Seven-times world champion Stephen Hendry is out of this year's tournament after he crashed to a 5-2 loss to Shaun Murphy, the 2005 Crucible champion.

Scot Hendry managed a high break of only 48, while Rotherham-based professional Murphy, the world number three, went through with runs of 87, 60, 63, 73 and 59.

He meets defending UK champion Ebdon, who pocketed breaks of 40, 48, 79, 83 and 49 in his own dominant display against Davis, who could only muster 76 points in total.

And the Englishman is in confident mood, saying: "I heard from a lot of the players that the tables were lightning-fast, which I thought helped. I thought my table was magnificent.

"I came here to have a decent run - and I feel as though I'm getting better with every match I play.