PARIS—French President François Hollande said Wednesday that three special forces soldiers were killed in a helicopter crash in Libya, in the first tacit acknowledgment that French troops are operating in the war-torn country.

Mr. Hollande said the three noncommissioned officers were killed when a helicopter carrying them had an “accident.” The president didn't elaborate on how the accident happened or provide details on the soldiers’ mission. A spokesman for Defense Minister Jean-Yves Le Drian said the troops were operating...