Athens champion Aldo Montano lost to fellow Italian Diego Occhiuzzi 15-13.
Also in the last 16, China's Zhong Man, the surprise winner at Beijing 2008, was beaten 15-10 by Hungarian Aron Szilagyi, Russian world number two Alexey Yakimenko went down 15-14 to American Daryl Homer and third-ranked Korean Gu Bongil lost by the same score to German Max Hartung.
Then, in the quarter-finals in front of a near full house, German top seed Nicolas Limbach crashed out 15-12 to Russia's Nikolay Kovalev.
In a surprise last four, it was Kovalev against Hungarian Szilagyi - a clash between the sport's ninth and sixth-ranked fencers - and Occhiuzzi against Romanian Rares Dumitrescu. They are ranked 14th and eighth respectively.