Chad says its armed forces have chased and killed 300 rebels who attacked a town near the border with Sudan.
Rebels attacked the town of Adre on Sunday, Chad said, but troops pursued them into Sudan before pulling out.
Previously, Chad said 100 rebels had died as its troops fought off their attack. Neither toll has been verified.
The attack on Adre, bordering Sudan's Darfur region, was the latest raid blamed by Chad on Sudan, which it says is fomenting unrest along the border.
Chad's Communications Minister, Hourmadji Moussa Doumgor, said Sudan was "wholly responsible" for the attack allegedly launched from its territory.
The charges were denied by the governor of the Sudanese region of north Darfur, Osman Yusuf Kibir, who said Sudan had never supported the Chadian rebels.
Several new rebel groups have begun operating in eastern Chad recently, led by mutinous military officers who say President Idriss Deby must step down.
The raid on Adre was the second attack in the area in just three days, the BBC's Stephanie Hancock in Chad reports.
Mr Doumgor said the rebels launched their attack on a garrison in Adre in 17 vehicles.
The Chad rebels want to oust Idriss Deby's government
The minister said the army launched a counter-attack, and the rebels were driven back, sustaining heavy casualties.
Aid workers in the western Sudanese province of Darfur reported hearing the sound of explosions and fighting coming from across the border.
Mr Doumgor said that Chad "holds the Sudanese government wholly responsible for this... attack, mounted from its territory".
He added that Chadian "government forces are now using their right of pursuit to ward off any further threat" against the border town.
Chad and Sudan have been recently trading accusations amid growing tension on their joint border.
Chad has accused Sudan of hosting rebels, while Khartoum has blamed N'djamena of deploying planes and troops on its territory.
In 2002, the government of Chad signed a peace agreement with one of the main rebel groups, operating in the east of the country.
The Chadian conflict has claimed several thousand lives since 1998.