For the first time since it captured El Fasher in late October, a Sudanese paramilitary group has allowed a trickle of aid into the ravaged city, giving a local humanitarian aid group the first outside glimpses into dire conditions there.

The paramilitary Rapid Support Forces has imposed a communications blackout on El Fasher since it seized the city and committed what witnesses described as mass atrocities against civilians. The city, in the western Darfur region, has been inaccessible to journalists, and aid groups and others outside the city have been unable to speak with the tens of thousands of civilians still trapped inside.

Malam Darfur Peace and Development, the local humanitarian group that gained entry to the city, brought food to 1,200 families in shelters in two deliveries, first last week and again on Thursday, it said in statements. The group said that residents are facing water scarcity, and an urgent shortage of medical services, “particularly for the many injured, elderly and ill individuals requiring immediate attention.”

“It is absolutely a disaster,” said Lukman Ahmed, the president of Malam Darfur Peace and Development. “People there are suffering. There is no food.”

“We hope this operation is going to attract others to come,” he added.

The group negotiated access to El Fasher with the Rapid Support Forces, or R.S.F. “We are hoping to have a big amount of food aid come into the city,” Mr. Ahmed said.

But the world’s biggest aid groups have not yet been able to reach El Fasher. For weeks, the U.N. has been negotiating with leaders of the R.S.F., which is fighting a two-and-a-half-year civil war against government forces, but has not been able to secure conditions for safe access.

“There is still ongoing military activity inside El Fasher. The security conditions are not there for us to access in a safe way for staff and partners,” said Ross Smith, the World Food Program’s director of emergency preparedness and response, in an interview.

“We do not have any food convoys going into El Fasher,” he added, saying that “we are prepared to move” once “minimum conditions” to enter the city are met.

The World Food Program said on Friday that it would be reducing rations in Sudan amid a severe funding shortage. Starting January, rations will be cut to 70 percent in famine areas and 50 percent for areas at risk of famine, what the group called “the absolute minimum for survival.” And even with those adjustments, the group says it has only enough resources to sustain current support for four months.

In November, senior R.S.F. officials pledged to allow the United Nations into El Fasher for the first time in months to deliver aid and to investigate atrocities. The U.N.’s humanitarian chief said that negotiations had made “useful” progress, and that the agency had received “strong agreement” from the R.S.F. for safe passage, but it has yet to happen.

Delivering aid in the war zone has been perilous. Missiles have struck past convoys, including a . Roads are tightly guarded with armed checkpoints, and Mr. Smith said aid groups had to navigate “heavily militarized zones with mines.” Witnesses have also told of looters stalking the routes.

Malam Darfur Peace and Development responded to public calls by the R.S.F. for aid, and obtained permission and security escorts to bring two convoys of food into the city, according to Mr. Ahmed.

“Sometimes you get a cup of tea in the morning. Sometimes you get something to eat,” Mr. Ahmed said of the people his group fed. “They are telling us ‘we are just staying here and having no food.’ We do not know how they are surviving.”

Even before El Fasher’s capture, conditions in the city were desperate. The R.S.F. besieged and bombarded the city for a year and a half. In that time, food, sanitation, social services and health care became dangerously scarce. In November, a satellite analysis by the Yale Humanitarian Research Lab found evidence suggesting that there were “no current patterns of life visible that are consistent with civilian presence and freedom of movement.”

After the R.S.F. overran the city, it unleashed a massacre, according to witness accounts and videos. The U.N. has collected reports of mass killings, sexual violence and detentions, and civilians reported fleeing through R.S.F. gunfire. The death toll is unclear, but some estimates run into the thousands.

Sudan’s civil war is widely considered one of the world’s worst humanitarian crises. The fighting has forced 12 million people from their homes and killed as many as 400,000 people, by some estimates.