Rebels in Chad said Friday they were fighting their way towards the capital Ndjamena and threatened to target any French aircraft flying reconnaissance missions over their positions.
But a Chadian government spokesman dismissed claims of a rebel advance.
The rebels alliance in the east of Chad called on France to stop flying intelligence missions in a statement read out to AFP by Ali Gueddei, spokesman for an alliance of rebel factions,
"We are making a last, solemn appeal to France for it to immediately cease its state of belligerence towards the armed forces of the opposition," said Gueddei reading a prepared statement by telephone.
France would be better advised to "stop its repeated provocations" in providing the government forces with intelligence through its aerial reconnaissance missions, said Gueddei.
France, which has had a military presence in Chad since 1986, supplied most of the troops for the European Union EUFOR peacekeeping mission in the east of Chad, on the border with Sudan and the Darfur region.
They are protecting not just the refugees from Darfur, but others from the Central African Republic forced from their homes by the fighting and displaced persons from Chad, numbering 450,000 in all.
But Gueddei warned that while the "opposition forces" backed EUFOR's work, the French had compromised that mission by its behaviour.
Earlier Friday, Gueddei said the rebel forces were pushing their way across the country towards the capital, after fighting broke out in the east with government forces.
"We are advancing. We have passed Goz Beida," 700 kilometres (430 miles) from Ndjamena, Gueddei told AFP.
On Thursday government helicopters attacked rebel positions in the east near the border with Sudan's Darfur region and Gueddei had claimed that guerrillas shot down one helicopter.
The Chad military insisted that the helicopter in question had simply been on a training flight and made an emergency landing due to mechanical problems.
"Slowly but surely we are moving towards Ndjamena," said Gueddei. "Ndjamena is our aim. It's no secret."
The government dismissed the claims of a rebel advance.
"Even with binoculars, we can't see them," said Communications Minister Mahamat Hissene, the government's spokesman.
"But seriously: we know that they have returned to Chadian territory and the army has taken all necessary precautions," he told AFP.
"We know their intentions. We have information that we don't want to reveal for the moment so as not to feed into this destabilisation campaign," he added.
Rebels attacked Ndjamena in February, reaching the presidential palace in an attempt to drive out President Idriss Deby Itno. A similar unsuccessful coup attempt was made in 2006.
But another rebel alliance spokesman, Abderaman Koulamallah, said the latest rebel force had some 500 to 600 vehicles and 7,000 to 8,000 men at their disposal, nearly double the number of the February offensive.
Since April, the army has largely had the upper hand in clashes in eastern Chad with extra resources deployed since February, according to European military officials.
Relations between Chad and Sudan have been difficult for over five years with the two countries regularly accusing each other of supporting rebels fighting against their respective regimes.
Diplomatic relations were broken off in mid-May after an attack near the Sudan capital Khartoum by a Darfur rebel group, the Justice and Equality Movement (JEM). Ndjamena denied any involvement.