The RadioShack-Nissan rider nipped in front of a group of sprinters, stealing a march and opening up a gap with 300m to go which he managed to hold on to win the 185km stage from Hoogerheide to Aalter..
The 23-year-old Italian held off Jurgen Roelandts (Lotto Belisol) on the line, with Manuel Belletti (AG2R La Mondiale) third, Arnaud Demare (FDJ-Big Mat) fourth and Tom Boonen (Omega Pharma-QuickStep) fifth.
Boonen's finish in the leading pack saw him retain the lead in the general classification.
At the Tour de l'Ain in France, Andrew Talansky (Garmin-Sharp) won the 157km fourth stage from Nantua to Septmoncel by six seconds from Rafal Majka (Saxo Bank).
Talansky's win saw him take a 12 second lead in the general classification.