A boy and his sister in a camp in Kolloye, Chad, are among the refugees left homeless by marauding militias along the border with Sudan.

Darfur War Spreads

Arab gunmen from Darfur have pushed across the desert and entered Chad, stealing cattle, burning crops and killing anyone who resists. The lawlessness has driven at least 20,000 Chadians from their homes, making them refugees in their own country.

Hundreds of thousands more people in this area, along with 200,000 Sudanese who fled here for safety, find themselves caught up in a growing conflict between Chad and Sudan, which have a long history of violence and meddling in each other's affairs.

"You may have thought the terrible situation in Darfur couldn't get worse, but it has," Peter Takirambudde, executive director of the Africa division of Human Rights Watch, said in a recent statement. "Sudan's policy of arming militias and letting them loose is spilling over the border, and civilians have no protection from their attacks, in Darfur or in Chad."

Indeed, the accounts of civilians in eastern Chad are agonizingly familiar to those in western Sudan. One woman, Zahara Isaac Mahamat, described how Arab men on camels and horses had raided her village in Chad, stealing everything they could find and slaughtering all who resisted.

The dead included her husband, Ismail Ibrahim, who tried to prevent the raiders from burning his sorghum and millet fields. Like so many others in this desolate expanse of dust-choked earth, she fled west with her three children, much as people in Darfur have been forced to do in recent years.

"I have lost everything but my children," she said, her face looking much older than her 20 years. She is now a refugee, with thousands of other displaced Chadians, in Kolloye, a village south of here.

"We have three bowls of grain left," she said. "When that is gone, only God can help us."

The spreading chaos is a result of two closely connected conflicts in the neighboring countries.

In Darfur, rebels have been battling government forces and the janjaweed, Arab militias aligned with the government, in a campaign of terror that the Bush administration has called genocide.

The United Nations Security Council has agreed to send troops to protect civilians, but they will take months to arrive. In the meantime, President Bush has said, NATO should help shore up a failing African Union peacekeeping mission there, but a surge of violence has chased tens of thousands of people from their homes in recent weeks.

In Chad, the government is fighting its own war against rebels based in Sudan and bent on ousting Chad's ailing president, Idriss Déby.

The rebels include disgruntled soldiers who defected and tribes tired of being ruled by members of the president's tribe, the Zaghawa, who represent just a small percentage of the population but have long dominated politics and the military.

In a sign of how inseparable the two conflicts have become, President Déby has accused Sudan of supporting the rebellion against his government, and Sudan has long suspected members of Mr. Déby's family of supporting Zaghawa-led rebels in Darfur.

Both sides agreed at a summit meeting in Libya in early February to stop supporting rebels on each other's territory and to tone down the belligerent talk. But Chadian rebels have remained on the Sudanese side of the border, and it is not clear whether Mr. Déby has the capacity to stop members of his clan from supporting Darfur rebels.

If unchecked by international intervention, this complex and volatile mix of government forces, allied militias and at least a half-dozen rebel groups in a remote region awash with weapons will almost inevitably lead to disaster, said John Prendergast, a senior adviser at the International Crisis Group, a nonpartisan nonprofit organization, and an expert on the Darfur conflict.