The Tigre, Gazelle and Apache helicopters destroyed about 20 targets and drew light arms fire, sustaining no damage, according to French military spokesperson Thierry Brukhard.
A Nato statement said the targets they hit included "military vehicles, military equipment and fielded forces". Other reports added a radar installation and a checkpoint to the list.
Flying from France's Tonnère carrier and Britian's HMS Ocean, they struck near the eastern port of Brega.
"The use of attack helicopters provides the Nato operation with additional flexibility to track and engage pro-Kadhafi forces who deliberately target civilians and attempt to hide in populated areas," the statement said.
It insisted that the operation was within the madnate of UN Security Council Resolution 1973, which authorised action to prevent attacks on civilians.
Helicopters can pinpoint smaller targets than fighter jets but are more likely to be shot from the ground because they fly lower.