French fighter jets struck targets in northern Chad on Sunday in support of local troops trying to repel a convoy of unidentified fighters that had crossed the border from Libya, France's military said in a statement.
"A Mirage 2000 patrol of the French armed forces intervened jointly with the Chadian army in northern Chad to strike a column of 40 pickups of an armed group from Libya infiltrating deep into Chadian territory," the armed forces said on Monday.
"This intervention at the request of Chadian authorities helped hinder this hostile advance and disperse the column."
The statement did not say who was behind the incursion, but it was the first time French forces have hit targets in support of Chadian troops since a fledgeling rebel movement based in southern Libya increased its activities last year.
The rebel movement, the Military Command Council for the Salvation of the Republic (CCMSR), was founded in 2016 and has fought Chadian forces several times near the Libyan border since August.
The group, which claims to have several thousand fighters, says its goal is to overthrow President Idriss Deby. Deby took control of Chad in 1990 in a rebellion that toppled then-President Hissene Habre.
French President Emmanuel Macron visited Chad in December and reaffirmed French backing for African anti-extremist forces amid growing international concern about the chaos in Libya.