France's military struck rebels in Chad to prevent a coup d'etat against President Idriss Deby, Foreign Minister Jean-Yves Le Drian said on Tuesday.
On Deby's request, French warplanes bombed a heavily-armed rebel convoy that crossed last week from Libya deep into Chadian territory.
"There was an attack by a rebel group that came from southern Libya ... to take power by force in N'djamena. President Deby asked us in writing to intervene to prevent a coup d'etat and protect his country," Le Drian told lawmakers.
The French jets destroyed dozens of pick-up trucks and the Chadian army subsequently said it had captured more than 250 rebels from the Union of Forces of Resistance (UFR), a Libya-based rebel coalition.
Deby has faced several rebellions since seizing power in 1990 in a military coup. International observers have questioned the fairness of elections that have kept him in office, and last year Deby oversaw a reform of the constitution that would allow him to stay in power until 2033.
France intervened in 2008 to stop the UFR toppling Deby.
President Emmanuel Macron has said he wants a new relationship with France's former colonies and that the era of propping up leaders in return for lucrative contracts for French companies -- a policy known as La Francafrique -- is over.
France, however, considers Chad's battle-hardened troops as vital in the fight against Islamist militants in West Africa and bases its 4,500-strong counter-terrorism Operation Barkhane force in the capital N'djamena
"This (intervention) was totally in line with international law," Le Drian said.
The incursion, which Chadian troops tried to halt, underscores how Deby's fight against Islamist militants in the region has stretched his military. The military effort has diverted finances away from public services and the economy, fuelling popular discontent in one of the world's poorest nations.