The U.N. refugee agency says 13,000 Congolese civilians have fled to Uganda over the past two days.

UNHCR said Thursday the new arrivals mean 27,000 Congolese have fled into Uganda since August.

Low-level fighting among armed groups has ground on for years in Congo's lawless North Kivu province, but violence sharply escalated in August.

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Rebel leader Laurent Nkunda says he is fighting to protect the country's tiny Tutsi minority.

All fighters in Congo have been accused of gross human rights abuses, including the government army.

In New York, the U.N.'s top Congo envoy told the Security Council that peacekeepers have opened several investigations into whether war crimes are being committed in eastern Congo.