Somali pirates in two skiffs fired on a French navy vessel early Wednesday after apparently mistaking it for a commercial boat, the French military said.
The French ship gave chase and captured five suspected pirates.
No one was wounded by the volleys from the Kalashnikov rifles directed at La Somme, a 3,800-ton refueling ship, French military spokesman Rear Adm. Christophe Prazuck said.
La Somme "was probably taken for a commercial ship by the two small skiffs" about 250 nautical miles off Somalia's coast, Prazuck said.
"They understood their mistake too late," he said.
One skiff fled, and La Somme pursued the second one in an hour-long chase.
"There were five suspected pirates on board. No arms, no water, no food," Prazuck said.
France is a key member of the EU's naval mission, Operation Atalanta, fighting Somali pirates in the Gulf of Aden.
It has aggressively tracked and caught suspected pirates and handed over at least 22 to Kenya.
An additional 15 suspects were brought to France for prosecution after allegedly seizing boats belonging to French nationals.
President Nicolas Sarkozy called for tougher action against piracy last year after dozens of attacks.