The United Nations refugee agency says up to 400 people may have been killed in attacks on two Chadian villages blamed on Janjaweed militia from Sudan.
The agency and local officials previously reported a much lower death toll from the attacks on the villages of Tiero and Marena late last month.
Tuesday, a refugee agency spokesman said aid workers who went to the villages found hundreds of homes burned to the ground and an overwhelming stench from the carcasses of dead animals.
He said residents are still finding corpses of people killed in the attacks, and that many who initially survived the attacks died later from dehydration or exhaustion.
The spokesman said the situation has stabilized following what he called a massive deployment of Chadian troops to the area.
U.N. agencies have expressed increasing concern about the situation in eastern Chad, where tens of thousands of people have been uprooted by increasing violence.
The government is fighting rebels in the area, and numerous villages have been attacked by armed groups believed to be Janjaweed. Sudan's government has been accused of arming the militia to suppress a rebellion in its Darfur region.
Some information for this report was provided by AFP.