Rebels in the Democratic Republic of Congo have surrounded the eastern city of Goma, in one of the sharpest escalations in years of conflict that has pitted the central African nation against neighboring Rwanda.

On Thursday morning, rebels from the Rwanda-backed M23 group captured Saké, forcing Congolese forces to retreat quickly, according to aid officials and eyewitnesses. It was the last major army position before Goma, the provincial capital of more than 2 million people.

The fall of Goma will be a major turning point for the group, which seized the city and held it for two weeks in 2012, but retreated after Rwanda came under intense international pressure to stop supporting the militia. The United States and the United Nations say Rwanda funds and directs M23, which Rwanda has denied.

In late 2013, the Congolese army and United Nations forces quickly defeated the rebel group, which then lay dormant for nearly a decade.

M23 has since returned, starting in late 2021, inflicting a series of heavy defeats on the Congolese army. At the same time, peace talks led by Angola, Congo’s southwest neighbor, are at a standstill, and the fate of the UN peacekeeping force, whose mandate was renewed in December for just one year, was up in the air until recently.

Goma, a hub for humanitarian organizations, UN agencies and foreign diplomatic missions in eastern Congo, has been a refuge for more than a million civilians fleeing violence by members of the M23 militia, Congolese forces and other armed groups in the region.

The rebels launched a major offensive this year, and now the city more and more cut off. The rebels control the country immediately to the north and west of Goma. To its east is the border with Rwanda. Its south is bounded by the coast of Lake Kivu.

Wounded civilians fleeing Saké arrived Thursday morning on foot and on motorcycles at a hospital in Goma run by the International Committee of the Red Cross. Abdourahmane Sidibé, a senior surgeon in the group, said he and his colleagues have treated twice as many civilians in the past few weeks than on average last year.

“There was too much bombing,” said Hawa Amisi, 52, who escaped with only a thin mattress, a bottle of water and her four children, who had nothing to eat. Mrs Amisi, who was separated from her husband in the fight, said she saw dead bodies lying on the street as they fled. “So many people died,” she said.

Bruno Lemarquis, the United Nations’ top humanitarian official in Congo, said 2025 would be a “difficult year” as humanitarian needs are likely to increase and funding is expected to decrease.

With peace talks collapsing in December, the attention of the distracted world dwindling and the United States — traditionally Congo’s biggest aid donor — expected to cut aid, aid officials and experts say there is a risk that one of the world’s biggest crises will become more neglected.

“Even before the arrival of the new US administration, we were told that US humanitarian aid would be cut by a third,” said Mr. Lemarquis.

Caleb Kabanda and Saikou Jammeh contributed reporting from Goma and Dakar.