Ronnie O'Sullivan, right, congratulates Ding Junhui after being defeated by Ding during their quarterfinal match at the the World Snooker Championship in Sheffield, England, April 27, 2017. [Photo/Xinhua]

SHEFFIELD, England - China's world number four Ding Junhui shocked five-time champion Ronnie O'Sullivan 13-10 to reach the semifinals of the World Snooker Championship on Wednesday.

Ding, last year's runner-up, built a 10-6 lead after two sessions on Tuesday but O'Sullivan won three of the first four frames in the final session, including a run of 146 in the 20th frame.

The Chinese star made an 87 to pull ahead 12-9 in the best-of-25 frames quarterfinal before O'Sullivan responded.

Ding, competing in his 11th world championship, gave no chance to the Rockets by killing off with a 117.