Foreign diplomats said they believed the downed plane was one of two aircraft, probably Italian-made Marquetti fighters, which Libyan leader Muammar Gaddafi had made available to Chad's military in recent days.
The plane's reported loss came a day after rebel forces were driven out of the town of Abeche which they had briefly seized on Saturday.
|Many rebels are based in western Sudan's lawless Darfur region|
Following the attack, civilians looted UN warehouses and government buildings, including the governor's residence.
The UN said looters had plundered around $1.5m worth of aid intended for refugees.
The UN and other agencies based in Abeche provide aid to 218,000 refugees from Sudan's Darfur, which neighbours eastern Chad, and some 90,000 internally displaced Chadians.
With the down in chaos, the rebels meanwhile looted government weapons stores.
Rebels said that a stolen Sam-7 anti-aircraft missile was used to shoot down the government aircraft on Tuesday.
Abeche is a major base for Chad's armed forces and is also used by a French military contingent, including a squadron of Mirage fighters, stationed in the central African country.
French assist Chad's government
As rebel forces advanced on Abeche at the weekend, France had ordered and deployed troops to protect the airport's perimeter.
|Al Jazeera filmed scenes of chaos at the weekend as the rebels entered Abeche |
In Paris, Jean-Baptiste Mattei, the French foreign ministry spokesman, told reporters on Monday: "These new rebel attacks show again the gravity of the situation and the urgency for an international presence to be deployed along the border between Chad and Darfur."
The rebels have been able to exploit volatility in neighboring Sudan, establishing rear bases in Sudan's troubled Darfur region.
Led by Mahamat Nouri, Chad's former defence minister, they say want to topple president Idriss Deby who they accuse of being corrupt.
The rebels tried to seize Chad's capital in April but were repulsed.