The reigning world champions currently lie third in Group A with one match to play, but they now know they will qualify in either second or third.
Pietro Figlioli, Valentino Gallo, Christian Presciutti and Danijel Premus each scored a brace for the Italians in their win.
Montenegro overcame Romania 12-8 in a hard-fought battle, Aleksandar Ivovic weighing in with a superb hat-trick.
Spain edged past Greece 11-9 to hold on to second place in their preliminary group with one match to play.
The 1996 Atlanta champions are guaranteed to qualify for the quarter-finals, but a higher group ranking could set up a more comfortable game for them.
Blai Mallarach, Felipe Perrone and Albert Espanol were all on target with a brace for Spain.
Serbia beat the USA 11-6 - although both teams are guaranteed a place in the quarter finals - while Hungary ran out 17-6 winners against Great Britain.