BEIJING, Aug. 21 (Xinhua) -- Hong Kong table tennis player Ko Lai Chak cruised into the men's singles top eight after disposing of German sensation Dimitrij Ovtcharov in the fourth round of the singles tournament on Thursday.

    Ko continued his good form to beat the 20-year-old Ovtcharov 11-4, 11-7, 11-4, 1-11, 11-1 to secure a berth in the top eight.

    "The match is the best I've played in this Olympics. Ovtcharov suddenly started to play long shots in the fourth set, and I attacked short in the fifth which made him scared to fight back," Ko said.

    Earlier on Thursday, Ko edged out defending champion Ryu Seung Min 4-2 to make the biggest surprise of the day.

    "I should have played better but my form dipped due to the tough match against Romaian Adrian Crisan in the morning. Ko played the best he can, " Ovtcharov said.

    Meanwhile, Croatia's 39-year-old vetern Zoran Primorac outlasted Yang Zi from Singapore 4-2 to keep his Olympic dream alive. World No. 1 Wang Hao claimed a comfortable 4-1 win over Kan Yo of Japan.

    "I was fortunate to play against the world's best player. Wang's overall level in playing is above me and he is more experienced," Kan said.

    The 5th-ranked Vladimir Samsonov of Belarus succumbed to Swedish veteran Jorgen Persson 3-4 (11-7, 11-8, 9-11, 13-11, 7-11, 10-12, 9-11) in a seesaw match.

    But two were at adds on the umpire's rule on a point in the sixth set. "I'm disappointed because I had a good chance to win. The ball is good and it hit the surface of the table," Samsonov said.

    "It was the toughest game I lost and I should have reached the top eight," he added.