Thousands of people fleeing a new rebel offensive could spread cholera and measles through eastern Congo in a rising threat to the devastated region, relief agencies warned Friday.

Doctors Without Borders said four children suffering from measles have died in the village of Birundule, which the group reached Thursday with a mobile clinic.

The agency is using sport utility vehicles carrying medical supplies, equipment and at least one doctor and one nurse to try to treat some of the tens of thousands of people hiding in forests or running from village to village to stay ahead of the fighting.

A rebel offensive against Rwandan Hutu militiamen drove 13,000 people into Uganda on Wednesday and Thursday.

Thousands are fleeing inside Congo. The doctors said they found thousands of refugees when a clinic went Thursday to the village of Lunysenghe, on the shores of Lake Edward.

"There is an estimated 5,000 displaced people, sheltering with the local population," said Salha Issoufou, a coordinator for Doctors Without Borders.

The U.N. Children's Fund said fighting in the town of Masisi on Thursday interrupted measles vaccinations for thousands of children.

"Cases of cholera (are) likely to spread to areas where the population moves," spokesman Jaya Murthy said. "The disease is spreading from frequent movement of people."

Both diseases can be easily prevented and treated but they become killers when people, especially children, have no access to medical care, are short of food and clean water and are crowded in unsanitary refugee camps.

Some refugees have fled three or four times in years of low-level fighting in eastern Congo that intensified with a rebel offensive launched Aug. 28. More than 250,000 people have abandoned their homes since then.

Rebel spokesman Bertrand Bisimwa blamed the Rwandan militiamen for this week's massive flight, saying they were telling people to leave the country.

"They are telling people we are criminals and want to kill them so that they will go away," Bisimwa said.

Renegade general Laurent Nkunda says his rebels are fighting to protect Congo's minority Tutsis from the Hutu militia that fled here after helping perpetrate the 1994 genocide that killed some 800,000 Tutsis and minority Hutus in Rwanda.

The militia, the rebels and Congo's government soldiers all are accused of grave atrocities against civilians.

U.N. peacekeepers have been unable to protect civilians or stop the fighting. The U.N. Security Council has agreed to reinforce its mission in Congo with 3,000 more soldiers and police because the current mission of 17,000 is spread too thin.

It has not been decided whether the additional troops would come from Europe or Africa.
At the Security Council on Thursday, France argued for a stronger mandate to allow the peacekeepers to more easily use force to protect civilians.