French warplanes struck a rebel convoy in northern Chad on Sunday, helping local troops repel an incursion across the border from Libya, a sign France's support for President Idriss Deby goes beyond fighting Islamist militants.
Mirage jets struck a column of 40 pickups carrying armed groups from Libya deep into Chadian territory, the French army said in a statement.
"This intervention at the request of Chadian authorities helped hinder this hostile advance and disperse the column," it said.
The strikes were the first by French jets in support of Chadian troops since the rebel Military Command Council for the Salvation of the Republic (CCMSR) based in southern Libya increased its activities last year in a bid to overthrow him.
The Union of Forces of Resistance (UFR), a rebel Chadian coalition created in 2009 after almost toppling Deby, said it was behind the offensive. CCMSR is a splinter group of the UFR.
"The aim is to bring Deby down," a UFR official said. "We thought France would not intervene in Chad's internal affairs, but it appears that it is offering no solutions for the Chadian people beyond keeping Deby in power to do their dirty work in the region."
The official said two fighters had been killed and two trucks destroyed.
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 since and last year he pushed through constitutional reforms that could keep him on office until 2033.
France considers its former colony as vital in the fight against Islamist militants in West Africa and based its 4,500-strong counter-terrorism Operation Barkhane force in the capital N'djamena where the United States also has a base.
But Deby's fight against Islamist militants - he has deployed troops to counter groups linked to al Qaeda and Islamic State in the Sahel and Lake Chad region- has strained his military and hit the oil-dependent economy, leading to growing dissatisfaction in one of the world's poorest nations.
"Deby remains the most viable and solid partner in the region. The Chadians are counting on France for the Libyan border," a French military source said.
Chad's military command said the operation had neutralized the column of "mercenaries and terrorists" in Chadian territory after earlier operations by the Libyan National Army.
The LNA, the military wing of one of Libya's two rival governments that operates in the east of the country under General Khalifa Haftar, began operations against Chadian rebels at the start of the year.
Haftar has close ties with France which has backed him against Islamist militants in Libya.