International observers say recent raids by Sudanese-backed Arab militias into neighboring Chad are severely threatening regional stability and the ability of humanitarian aid workers to reach more than a million starving people displaced by fighting in Darfur in western Sudan.
The Brussels-based International Crisis Group says recent reports of Chadian troops clashing with Janjawid Arab militias in Chad show that the Sudanese government is blatantly ignoring international calls to end its support of the militias in Darfur.
Human rights groups have accused the Arab Muslim government in Khartoum and the Janjawid militia of committing ethnic cleansing in the region, driving out more than one million black Africans from their homes.
"At the end of the day, the government is the body that is responsible for the Janjawid," said David Mozersky, a Sudanese affairs expert at the International Crisis Group. "They have been supporting them. They have been arming them. They work in close coordination with the Janjawid in military operations and it is their responsibility to control them. They have not done that."
On Sunday, officials in Chad told reporters that hundreds of Janjawid militiamen carried out three separate attacks on villages last week on the Chadian side of the border, sparking at least two gun battles with Chadian troops.
The most intense fighting took place on Wednesday, when 60 militiamen, a Chadian soldier and six Chadian civilians were reportedly killed.
The Janjawid is helping the Sudanese government fight rebel groups in Darfur.
Mr. Mozersky at the International Crisis Group says although the Janjawid have made similar raids into Chad in the past few months to attack refugee camps and steal livestock, engaging Chadian troops is a new development that could significantly raise tension between the two countries.
Mr. Mozersky predicts that if the militia attacks continue and Chad retaliates against Sudan, humanitarian efforts to save more than a million people in Darfur and another 100,000 along the border in Chad could be crippled.
The United Nations says the situation in the region is already the worst humanitarian crisis in the world. The organization has appealed for $115 million in aid for displaced people in Darfur and another $30 million for refugees in Chad.
"The crisis really is a threat not only to Sudan but also to the regime in Chad and this escalation of violence between the governments is very worrisome because so many things need to go right for the humanitarian situation to be dealt with," Mr. Mozersky said. "Any further complications [or] confusions at this point are going to make an adequate humanitarian response from the international community that much more difficult."
Until last week, Chad had worked mainly as a mediator to end the conflict in Darfur, which erupted 15 months ago.
On April 8, Chadian President Idriss Deby helped broker a cease-fire between the Sudanese government and the two main rebel groups in Darfur to allow the flow of humanitarian aid to begin.
An African Union assessment team is currently in Darfur, attempting to lay the groundwork for observers to monitor the cease-fire.