Rebels in the Democratic Republic of Congo have surrounded the eastern city of Goma, in one of the sharpest escalations in years of a conflict that has pitted the Central African country against its neighbor Rwanda.

On Thursday, fighting raged between rebels from the Rwanda-backed M23 group and Congolese forces in the town of Saké, the last major army position before Goma, a provincial capital with more than 2 million people. On Tuesday, M23 captured Minova, a key town along one of Goma’s main supply routes.

Goma’s fall would be a major milestone for M23. The group captured the city and held it for two weeks in 2012, but withdrew after Rwanda came under intense international pressure to stop backing the militia. The United States and United Nations say Rwanda funds and directs the M23, charges that Rwanda has denied.

In late 2013, the Congolese Army and United Nations forces quickly defeated the rebel group, which lay dormant afterward for almost a decade.

M23 has since surged back, starting in late 2021, dealing the Congolese Army a series of defeats. At the same time, peace talks spearheaded by Angola, Congo’s southwestern neighbor, have stalled, and the fate of U.N. peacekeepers stationed in eastern Congo was until recently up in the air, with their mandate renewed in December for another year.

Goma has long been a refuge for more than a million civilians fleeing violence from M23 militiamen, Congolese forces and other armed groups in the region.

The rebels launched a major offensive in eastern Congo this year, and now the region is increasingly cut off. Rebels control the land immediately to Goma’s north and west. On its east lies the border with Rwanda. Its south is demarcated by Lake Kivu.

Rebels have also made gains in other parts of North and South Kivu provinces, which include two other major cities, Butembo and Bukavu. M23 has made the capture of Kavumu airport another main objective, according to U.N. intelligence. Government-allied troops have used the airport to support the Congolese armed forces.

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

“There was too much bombing,” said Hawa Amisi, 52, who fled with only a thin mattress, a bottle of water and four of her children. Ms. Amisi, who had been separated from her husband in the fighting, said she saw dead bodies lying in the street as they fled.

Bruno Lemarquis, the United Nations’ top humanitarian official in Congo, said 2025 would be “a difficult year” because humanitarian needs are likely to rise, and funds are expected to dwindle.

The United States — traditionally Congo’s largest humanitarian donor — is expected to slash aid under the new Trump administration, humanitarian officials and experts say. “Even before the new U.S. administration came in, we were told that U.S. humanitarian support would be slashed by a third,” Mr. Lemarquis said.

The conflict in eastern Congo — an area about the size of Michigan — was once labeled Africa’s World War. It has been going on since the 1990s, and has involved dozens of armed groups, of which M23 is currently dominant.

Rwanda claims M23 is fighting for the rights of Congo’s Tutsis — the ethnic group targeted by extremists from Rwanda’s Hutu majority in the 1994 genocide in which more than 800,000 people were killed.

But many Congolese see the rebel advance as an invasion of their country by a foreign power.

Now equipped with high-tech weapons, according to a recent U.N. report, M23 rebels are trying to establish a long-term presence in the region. They train police, set up courts, collect taxes and issue birth certificates, experts say, and have assassinated several traditional leaders, replacing them with officials favorable to their cause.

Most observers say M23 wants land and Congo’s valuable rare minerals such as coltan, a metallic ore used to produce tantalum, which is in smartphones and laptops. Last April, M23 seized mines in Rubaya — one of the world’s biggest sources of coltan.

As the rebels have conquered more territory over the past few years, the violence has reached new heights.

Thousands of children have been killed, maimed and forced to become child soldiers. Serious injuries caused by heavy artillery have increased. Many of the victims are children.

Sexual violence has reached extreme levels. In 2023, Doctors Without Borders treated more than 25,000 survivors of sexual violence — the highest number ever recorded in the country. Numbers for the first half of 2024 were even higher.

More than 240,000 people have been forced to flee from their homes since the start of this year, according to the United Nations’ refugee agency, as M23 rebels have launched new offensives in the eastern regions of North Kivu province, where Goma sits, and South Kivu. They join 4.6 million people who were already displaced in Congo’s east.

Saikou Jammeh contributed reporting from Dakar, Senegal.