The 36-year-old, a triple Olympic medallist in team competitions, battled past China's Lin Gaoyuan in the last eight at the GETEC-Arena in Magdeburg.

Boll won 11-7, 11-9, 13-15, 11-7, 14-12 on a day when the men's draw also had to play their second round matches.

The German's opponent in the semi-finals will be South Korea's Lee Sangsu, who caused a shock by knocking out world number four Xu Xin of China.

Lee, the 14th seed at the ITTF World Tour event, did not drop a game as he beat the Rio 2016 Olympic team gold medallist 11-6, 11-9, 11-4, 12-10.

"I'm very happy to win, but I think he's not playing with as much power," said Lee. 

"I think his last match with Marcos Freitas was too tiring, he won 4-3, played a lot of forehand and moved a lot, so I think this match he wasn't 100 per cent. 

"So even though I'm very happy to win, it's 80 per cent happiness and 20 per cent mixed feelings."

A second home player remains in contention with Germany's Dimitrij Ovtcharov a 11-1, 5-11, 11-5, 7-11, 11-4, 11-3 winner over Hong Kong's Wong Chun Ting.

Ovtcharov, who has already won three World Tour gold medals this season, will now lock horns with top seed Fan Zhendong, the Chinese player who beat Japan’s Kenta Matsudaira 11-8, 11-6, 11-5, 8-11, 11-9. 

The women's draw only had to play their last eight matches today and three of the four winners came from China.

World number one Zhu Yuling knocked out compatriot Wang Manyu 11-0, 13-11, 7-11, 6-11, 11-8 as the triple world champion seeks to clinch German gold.

She will play Japan's Kasumi Ishikawa who prevented an all-Chinese semi-final line-up by beating defending champion Wu Yang 11-4, 11-7, 11-8, 11-3.

Feng Yalan beat Japan's Mima Ito 11-6, 11-13, 4-11, 7-11, 9-11 to set up a clash with team-mate Chen Meng, a 9-11, 11-4, 11-5, 9-11, 6-11, 11-5, 14-12 victor against compatriot Chen Ke, a qualifier. 

The semi-finals and finals will be played tomorrow with doubles events also concluding.