Sudan's government has denied claims that it supports cross-border raids on villages in neighbouring Chad.
Chad and Sudan have traded insults over border town clashes
Some of the violence is being blamed on Chadian army deserters who have based themselves in Sudan's western Darfur region in recent months.
The New York-based group Human Rights Watch says most attacks were by militia from Sudan and Chad, apparently with some Sudanese government backing.
The government said Sudan was disarming those Chadian insurgents they found.
"HRW is always telling stories, taking it from third or fourth hand information," the minister of state for foreign affairs, Samani al-Wasiyla said
"We have the African Union from two days ago at a news conference saying they are very sure Sudanese troops have nothing to do with it."
A report published on Sunday said that tens of thousands of people had been displaced within Chad due to almost daily militia attacks.
HRW researchers said they had documented numerous attacks on villages just inside Chad by militias who had crossed the border from Sudan.
They said the militias killed civilians, burned villages and stole cattle.
The BBC's Jonah Fisher says it is a sensitive time for Sudan with the peace talks with Darfur rebels entering a final phase.
The claims also come as the Khartoum government comes under increasing pressure to allow the United Nations to take over the peacekeeping mission in Darfur.
Pro-government Janjaweed militiamen are accused of killing thousands of civilians in attacks on villages in Darfur and forcing 2m people to flee in reprisals following a rebel uprising in the region.
Currently some 7,000 troops from the African Union are attempting to maintain security across the huge Darfur region.
However, funding is running out and the UN Security Council is discussing changing this to a UN peacekeeping operation. HRW said any such UN mission should have a strong mandate to protect itself and civilians, by force if necessary, and to disarm and disband the Sudan government-sponsored militia.
Libyan officials are reported be planning to hold a mini-summit on Wednesday to try and ease tensions between Chad and Sudan.