Karlsson had been expected to depart the competition in the first round as he came up against home favourite Dimitrij Ovtcharov of Germany, who he had never beaten at a world rankings event.

That record was soon wiped out, however, as Karlsson fought back from a difficult start to overcome the world number four 6-11, 11-7, 11-5, 11-5, 13-11 to earn one of the best wins of his career to date.

Karlsson then took on Frenchman Simon Gauzy, who saved three match points in his opening clash with Germany's Bastian Steger, in the last eight and battled to a marathon victory to reach the last four.

The Swedish player was involved in a topsy-turvy contest with Gauzy before he eventually prevailed with a  5-11, 11-8, 11-4, 10-12, 11-7, 8-11, 12-10 success.

"This victory means a lot to me because in the first game, he started attacking me and if you allow him to attack you first you will find it difficult to beat him," Karlsson said following the win against Ovtcharov.

"In the second game, I became more aggressive and this really worked for me. 

"I made sure I took all of my chances in the game."

Karlsson will need to cause another upset if he is to progress further at the tournament as he is due to take on world number two Fan Zhendong of China in tomorrow's first semi-final.

Fan, who has a point to prove after he was not chosen for the Chinese team at the recent Olympic Games in Rio de Janeiro, breezed into the last eight by beating Gao Ning of Singapore 11-3, 11-3, 11-6,11-3.

The Chinese star then made light work of South Korea's Jung Young-Sik with a 6-11,11-5, 11-9, 12-10 ,11-9 victory.

Wong Chun Ting of Hong Kong will go up against China's Xu Xin in the other semi-final.

Wong beat South Korean Lee Sangsu, who had earlier accounted for Belarusian Vladimir Samsonov, in straight games, 11-9, 11-5, 11-7, 11-5, while Xu ended the run of Gerell Par of Sweden with an 11-7, 7-11, 8-11, 4-11, 7-11 win.