The fighters and two military sources reported that, this week, the rebels in northern Chad attacked the government forces on the border with Libya. The government has denied the incident.
A nascent rebel movement, the Military Council of the Command for the Salvation of the Republic (CCMSR), says it wants to depose President Idriss Deby, who has come to power since.
Deby, 66 years, has faced several revolutions since the 1990 took office, leading an insurrection that overthrew President Hissene Habre. Deby was an ally of the West in the fight against Islamic militants in West Africa.
The CCMSR, which claims to have 4.500 fighters, was founded in 2014 and fought its first battle against government forces earlier this month in the mining town of Kouri Bougoudi.
Among its ranks are former rebels from the Darfur region of neighboring Sudan and former political allies of former president Habre, who is serving a life sentence in a Senegalese prison for war crimes and crimes against humanity.
The CCMSR claimed that its fighters, once again, attacked the Chadian soldiers in Kouri Bougoudi in the most brutal way on Tuesday morning morning.
Security Minister Ahmat Mahamat Bachir denied that the rebels attacked the army, but two Chadian military sources told Reuters there were fighting. Neither the CCMSR nor the sources provided any information on the incidents.
The nascent rebellion is the latest headache for the security of Chad, which closed the border with Libya in January, hoping to prevent its militants from entering. Chad also faces threats from groups linked to al Qaeda and the Islamic State.