Rebels in Chad have warned the nascent European Union peacekeeping force they will fight it as a "foreign occupation army" if it sides with President Deby.
These rebels were captured after Monday's battle
The warning from the rebel Assembly of Forces for Change (RFC) follows a major battle with a different rebel group which shattered a month-long ceasefire.
The clashes were near the area where 4,000 EU peacekeepers are to be sent - the border with Sudan's Darfur region.
The government says the attackers were chased to the border and wiped out.
The BBC's Stephanie Hancock says latest reports from the area say there has been renewed heavy fighting in the past few hours.
UFDD spokesman Mahamat Hassane Boulmaye told our correspondent that fighting had resumed.
Chadian army sources, who asked not to be named, also confirmed renewed clashes after an army column advanced from a garrison town near the border with Sudan, to attack a rebel stronghold.
Both the Union of Forces for Democracy and Development (UFDD) rebels and the government say that hundreds of fighters have been killed in this week's clashes.
Chad's government said earlier it had tracked down and destroyed the remnants of the UFDD rebels but their leader Mahamat Nouri had crossed the border into Sudan on foot.
The government has always accused Sudan of arming the UFDD and is now calling on the government in Khartoum to find Mr Nouri and return him to Chad to face justice.
Sudan has previously denied having links to Chad's rebels.
"As far as Chad is concerned, the UFDD has been completely destroyed," government spokesman Hourmadji Moussa Doumgor said after clashes on Wednesday.
Fierce fighting broke out on Monday between the town of Abeche and the Sudan border.
Both the RFC and UFDD were among the four rebel groups who signed up to a Libya-brokered peace deal just last month.
EU force delays
The proposed EU force has been hit by delays and fears that its French contingent may not be seen as neutral, given France's support for Chadian President Idriss Deby.
"The strong involvement of the French is naturally being seen with some scepticism here and there," Austrian Defence Minister Norbert Darabos said.
Villagers help government soldiers bury their dead
Austria is one of the EU contributor nations to the force, which was initially scheduled for deployment this month.
The delay is reportedly because contributor nations have yet to commit to supplying the required numbers of troops and logistical resources such as aircraft and medical support.
On Wednesday, Ireland became the latest country to approve its contribution of 400 troops as well as the force leader, Lt Gen Patrick Nash, but the Irish are not expected to arrive in Chad before January or February next year.