The Sudanese military says 17 of its soldiers were killed late Monday during a raid by the Chadian army on a Sudanese border town.
A Sudanese army spokesman says Chadian troops attacked the Fur Baranga area, using land cruiser vehicles and tanks. He said Sudanese forces pushed the attackers back across the border, but took casualties that also included 40 people injured.
Chad's government has denied that its forces crossed the border.
Earlier Monday, the Chadian army clashed with rebels in eastern Chad. Chad's information minister, Hourmadji Moussa Doumgor, said the rebels crossed over from Sudanese territory to attack a village, Amdjerima, where government troops were based. He said eight Chadian soldiers and many rebels were killed.
Chad and Sudan have repeatedly accused each other of supporting rebels in their respective countries.
Both countries have refused the deployment of international peacekeepers on their border.
Eastern Chad has witnessed increasing violence over the past year, as the government continues to fight the rebels, and violence spills over from Sudan's neighboring Darfur region.
Tuesday, the U.N. refugee agency reported that up to 400 people may have been killed in two Chadian villages last month during attacks blamed on Sudanese Janjaweed militia.
The violence has forced tens of thousands of people to seek refuge in camps run by aid groups and the United Nations.
Some information for this report was provided by AFP, AP and Reuters.