Ronnie O'Sullivan produced a strong burst to get the better of Mark Williams 13-10 and so advance to the semi-finals of the Betfred World Snooker Championship at the Crucible. 

Trailing 6-2 after the first session, the five-time champion found some momentum to draw level 8-8 ahead of the final session.

On the resumption, Williams edged back in front as he pounced on a loose safety from O'Sullivan to make a 42 break.

O'Sullivan's frustration began to show in the next frame but he rallied to haul immediately back level, only for Williams to snatch the next frame when 'The Rocket' missed a red to end a break of 52.

A dazzling 103 brought O'Sullivan level and he moved ahead for the first time in the match with breaks of 61 and 65 in the next.

His fifth century of the match - a 133 total clearance - moved O'Sullivan within one frame of victory and he sealed a 13-10 win on a re-spotted black in a remarkable end to the 23rd frame in which he had previously missed a simple blue for the match.

In a repeat of the 2014 final, O'Sullivan will face Mark Selby in the last four. Earlier, Selby defeated Neil Robertson in their last-eight clash. 

It's a match that a somewhat mischievous O'Sullivan is looking forward to when he spoke to the BBC. "I love a semi! I'd lump on Selby because I don't expect to beat him, and that's not me trying to take the pressure off, I don't need to I've got nothing to prove.

"Just as a bit of insider information from me... I don't know how anyone can beat him."

In the other semi, Kyren Wilson, who defeated defending champion Judd Trump 13-9, will take on Anthony McGill. 

The latter, who led 7-1 and then 9-3, was forced to hold off a spirited fightback from Norway's Kurt Maflin in the battle of the qualifiers.

While the Scot won the first frame of Tuesday evening's session to go 11-6 up, Maflin then won four of the next five frames before McGill wrapped up a 13-10 win.