U.N. observers encountered about 100 Rwandan troops in eastern Congo, a U.N. official said Wednesday, marking the first confirmed sighting since Rwanda threatened to send in its forces against Rwanda Hutu rebels sheltering here. The Rwandan forces withdrew toward Rwanda after Tuesday's encounter, said M'hand Ladgouzi, head of the U.N. mission at Goma. He spoke at a news conference in Goma, the largest city of the east.