Three Clermont Auvergne players have been hospitalised after being attacked with machetes and swords as they walked back to their hotel early on Sunday morning.
France internationals Aurelien Rougerie, Julien Pierre and Benjamin Kayser were all taken to hospital after "a dozen" armed men attacked them in the southern town of Millau.
Pierre is to undergo surgery on "deep cuts" to his hip, but none of the injuries suffered by the trio are life-threatening.
A statement published on Clermont's official website read: "While returning on foot to their hotel overnight from Saturday to Sunday, a group of Clermont players was attacked by a dozen individuals armed with machetes, knives and swords.
"A police investigation was opened immediately in Millau, where the Clermont players were staying before travelling to Falgos (a training camp) for a few days.
"Following the attack, Benjamin Kayser (arm injury), Aurelien Rougerie (arm injury) and Julien Pierre (hip injury) had to be hospitalised.
"Their lives are not at risk but the Clermont lock (Pierre) needs to undergo surgery to treat deep cuts."
Wing and centre Rougerie, 33, is Clermont's captain and has 76 caps for France. Hooker Kayser, 29, has played 24 times for France and Pierre, 33, has 27 caps.
The Top 14 club, who said they were "shocked and outraged" by the attack, pledged to assist local authorities in "finding and punishing the perpetrators".
The statement continued: "In addition to any complaints from the individual players involved, the club will also consider pursuing its own judicial proceedings.
"We will provide more information on the health of our players as soon as possible."