World Championship 2017: Mark Selby & Ding Junhui level at 12-12 in semi-final

Mark Selby and Ding Junhui are all square at 12-12 in their thrilling World Championship semi-final.

China's Ding made centuries in the final two frames of the third session, having responded to breaks of 128 and 64 by defending champion Selby.

Selby fell 5-3 behind in the match, a repeat of last year's final, but took four in a row to start session two and then led 10-7 before Ding's revival.

The best-of-33 tie will be played to a conclusion from 14:30 BST on Saturday.

Before that, four-time champion John Higgins and 2013 finalist Barry Hawkins will resume at 10:00 BST with the Scot 10-6 ahead.

Higgins had been 5-3 ahead after the first session and, although not playing at his best, he managed breaks of 89 and 53 to frustrate the Englishman.

Ding shows new lease of life

Ding did not seem rattled at losing his early lead

Last year's runner-up Ding might have felt he had missed his big opportunity to get back on terms in the 22nd frame, when he was 50 points ahead with 67 remaining, but a missed red to the middle pocket proved costly as Selby snatched the frame on the black.

In the past, being behind has seemed to knock Ding's confidence, but he has shown a mental toughness in this tournament, in which he has overcome two fellow Chinese opponents and five-time winner Ronnie O'Sullivan.

He maintained his composure to end the evening with stunning breaks of 117 and 128 to leave the match tantalisingly poised going into the final session.

He did not have it all his way though. While Thursday's first session was mostly free-scoring, with Ding compiling breaks of 110, 84 and 76 to go ahead, he was left to suffer in the second session after being worn down by his opponent.

Snooker's attritional specialist Selby has the ability to cross the line in the long, drawn-out struggles and has taken all five frames that have lasted over 30 minutes, while also showcasing his high-scoring ability with seven breaks over 60, including two centuries.

Higgins plays hardball

Higgins last won the World Championship in 2011

Higgins has reached this stage of the competition for the first time since he last lifted the trophy in 2011 and has put himself in a strong position to progress to a sixth Crucible final.

The winner of 28 ranking titles was 65-0 ahead in the final frame of the second session but saw his opponent hit back with some precise tactical play.

However, a mistake on the blue allowed an easy long pot for Higgins to prevail in a crucial 40-minute battle.

It opens up a four-frame advantage and leaves free the prospect of a repeat of the 2007 final, which Higgins claimed by beating Selby.