The UN reported Thursday that thousands of civilians had fled a battle zone in the eastern Congo near the Rwanda border, heightening fears that the Congo war, which has claimed as many as 3 million lives, may be erupting once more.
But the Rwandan government, which played a crucial role in the hostilities that began in 1998 and, officially at least, ended early last year, rejected what UN observers called "corroborating clues" that its troops had entered eastern Congo, defying a recent international peace agreement.
The UN mission in Congo told news services that it had aerial photographs and ground sightings indicating that Rwandan troops had crossed the border into Congo. The evidence included encounters with soldiers who appeared to carry Rwandan military gear and the sighting of a group of about 100 soldiers who appeared to be of Rwandan origin.
UN officials also were quoted as saying that thousands of civilians had fled the area around Goma, in eastern Congo, amid fierce fighting between Rwandan rebels and an unidentified force.
Richard Sezibera, an adviser to Rwanda's president, Paul Kagame, said at a news conference on Thursday that reports of Rwandan troops entering Congo were false.
He added, however, that "if it became necessary in the defense of Rwandan territory, her sovereignty and her people and in pursuit of genocidal forces in the territory of the Democratic Republic of Congo, Rwanda would be forced to enter."
A Rwandan incursion would be a major setback for international efforts to resolve the conflict in Congo, which in the past year has drawn in the military forces of at least seven neighboring nations on both sides.
Twice before, in 1996 and 1998, Rwanda's Tutsi-led government has sent troops into Congo for the stated purpose of routing Hutu rebels, at least some of whom are former Rwandan soldiers who participated in the massacre of 800,000 Rwandan Tutsi and moderate Hutu in 1994.
The UN has mounted an effort with Congolese and Rwandan officials to disarm the Hutu rebels, but Rwandan officials say the disarmament effort has moved too slowly and that the rebels frequently have attacked Rwandan territory.
Some private analysts say, however, that Rwanda wants to promote instability in the region to increase its control of the area's rich natural resources, which include diamonds, gold and coltan, a crucial ingredient in cell phone circuit boards.
The UN has accused Rwanda, Uganda and Burundi of stealing vast quantities of coltan from Congo, which holds some 80 percent of the world's known reserves of the mineral.
Sezibera, the Rwandan president's adviser, dismissed those accusations as part of what he said was a smear campaign by Western analysts and Congolese officials against the Rwandan government.
On Thursday the EU's foreign-policy representative, Javier Solana, warned Rwandan officials that an invasion of eastern Congo would violate both international principles and a Nov. 20 agreement among 14 of the region's nations to work toward peace in the troubled region.