A spokesman from one of the two main rebel groups fighting the Sudanese government in the rebellious Darfur region said the militia attack on a refugee camp and local villages occurred on Wednesday and left four people dead.

Quoting official Chadian sources, the BBC reported that after the militia attack on refugees inside Chad, Chadian troops pursued the militiamen back into Sudan. Chadian soldiers then skirmished with Sudanese troops.

If confirmed, this would be the first such clash between regular troops from the two neighbouring countries

"Militia forces crossed over the border to Beir Ruswan, 10km into Chad. They attacked a Sudanese refugee encampment and the host communities and they looted cattle," said the Sudanese Liberation Army's (SLA) Muhammad Mursal.

Villagers killed

Mursal said four villagers were killed in an exchange of fire with the militiamen, who are known as the Jinjawid.

A Chadian military source confirmed "there was a confrontation between the Sudanese militias and Chadian forces in the east".

Both rebel groups, SLA and the Justice and Equality Movement, signed a truce earlier this month with the Sudanese government to allow urgent aid to about one million people affected by the conflict raging in western Sudan.

An estimated 10,000 people have died in the rebellion in the Darfur region.

UN officials have said the situation in Darfur is one of the world's worst humanitarian crises, with more than 110,000 refugees having taken shelter in neighbouring Chad.