Got your scorecard out? Quick, which side is the US backing here? From Reuters, Dec. 9:

N'DJAMENA - The Chadian army clashed with rebels in eastern Chad on Saturday during several hours of heavy fighting in the desert, rebel and government sources said.

The battle took place some 50 km (31 miles) outside the prefectural capital of Biltine, which rebels from the Union of Forces for Democracy and Development (UFDD) took on Thursday, before withdrawing a day later in the face of an army advance. Rebel leader Mahamat Nouri told Reuters three columns of army vehicles had cornered his troops in a dried out riverbed, and attacked from two sides.

In four hours of fighting, he said the rebels repelled the government troops, killing more than 200 of them compared with only around 50 dead in their own ranks.

"The Chadian national army was routed. It was a debacle for government forces," Nouri said.

A Chadian government military source confirmed several hours of heavy fighting outside Biltine starting at 0600 GMT, but declined to estimate casualty figures.

Over the last year, several rebel groups dedicated to toppling President Idriss Deby have fought a low-intensity war in the desert, mountains and scrubland of eastern Chad, occasionally striking further west.

In April, the rebels reached N'Djamena -- the western capital of the landlocked oil-producer -- but were repulsed after hundreds of people were killed in fighting. Former fighter pilot Deby, in power since 1990, won a new five-year term at elections boycotted by the opposition just a few weeks later. Chad says the rebels are mercenaries supported by neighbouring Sudan. It says the conflict in Sudan's western Darfur region is spreading rebels and Arab militia raiders across the region, destabilising central Africa.

See our last posts on the politics of the Sahel and the escalating crisis in Chad.