Ronnie O'Sullivan's quest for an eighth Masters title continued as he reached the semi-finals with victory over Ryan Day.

The 43-year-old recorded his 989th career ton and six half-centuries in a 6-3 win over Day at Alexandra Palace.

Day was holding his own, sharing the first four frames, before O'Sullivan's 119 break saw him take the lead.

The Welshman fired back with a break of 77 and, after O'Sullivan made it 4-3, was in control of the penultimate frame.

But Day could not convert a 66-point lead as O'Sullivan's break of 78 saw him move one away from victory, which was sealed with a 92 break. 

He will face Ding Junhui, who beat Belgium's Luca Brecel 6-5 despite forfeiting a frame.

Brecel led 35-0 in the ninth and the players were engaged in a bout of safety play when Ding attempted to hit a difficult red when he had other options.

After missing twice he was warned by the referee that he had to hit it at his next attempt. He duly missed and forfeited the frame as he wasn't in a snooker at the time.

This left him trailing 5-4, but it didn't hold him back and he went on to win a high-quality quarter-final by taking the last two frames.

"I thought a lot of how to play it and felt this was the best shot to play. Maybe I was too confident that I was going to hit it," he said.