GOMA, Congo — Rebels believed to be backed by Rwanda began retreating from the territory they seized last week and pulled out of the region of Masisi, their military leader said Wednesday, in the first concrete sign that international pressure has curbed the advance of the fighters.

General Sultani Makenga, the military chief for the eight-month-old rebellion known as M23, said his fighters intend to abide by an ultimatum issued by neighboring nations that called for their withdrawal from Goma by Friday. He said he had ordered his fighters to retreat along the southeastern axis from Masisi to Goma, and they will then leave Goma via the northern route to Rutshuru.