Government forces and rebels in Chad have been clashing northeast of the capital N'Djamena, prompting the former colonial power France to send in reinforcements to help the army. Rebels say they want to overthrow President Idriss Deby if he does not accept a power-sharing deal. VOA's Nico Colombant reports from our West Africa bureau in Dakar.

Fighting with heavy artillery started in the morning hours, Friday, about 100 kilometers northeast of the capital, around the town of Massakory.

Government officials say they were able to easily push back the rebel offensive, making what they called "mercenaries from Sudan" flee back into the desert.

Rebels taking part in the offensive said they had been able to set fire to dozens of army tanks and vehicles and were pushing toward the area of Massaguet, about 80 kilometers from the capital on the main road. There was no independent confirmation on details of the fighting.

Rebels also said they had columns ready to advance on N'Djamena from other directions. Many rebel leaders are former close associates and relatives of Mr. Deby.

An exiled rebel spokesman, Makaila Nguebla, says President Deby must negotiate a power-sharing deal, resign or face continuous rebel assaults.

Nguebla was angered by the troop reinforcements sent in by the former colonial power France.

He said it was another trick to keep Mr. Deby in power. He says he does not understand why France wants to impose what he called a "dictatorship" on the Chadian people.

France has a defense treaty with Chad which allows it to have a permanent military base in the capital. The French Defense Ministry said it had sent in an additional 150 troops to Chad as a precaution to help respond to the spiraling situation.

The French military said its Mirage jets and soldiers were helping Chadian government troops with logistics, surveillance and medical support, but not engaging in combat with rebels.

In N'Djamena, mobile phone networks were disrupted. Schools and many offices were closed. Many residents tried to stock up on provisions, while helicopters clattered overhead. The military also set up roadblocks in strategic areas.

Mr. Deby, a former rebel, took power in a coup in 1990. He changed the constitution to allow unlimited presidential mandates. Mr. Deby accuses Sudan of backing the Chadian rebellion. Sudanese officials deny this, and accuse Mr. Deby of backing rebels in Sudan's warring Darfur region.