The civilian death toll is climbing and concern over a broader conflict is growing as rival generals vie for control of Africa’s third-largest country.

Sudan’s nightmare scenario is coming to pass.

Fighter jets screamed over Khartoum, the capital, on Sunday, firing rockets into a city of millions. Artillery barrages slammed into the military headquarters, reducing it to a tower of flames. Civilian planes were bombed at the city’s airport, where terrified passengers cowered on the terminal floors.

The country has been walking a tightrope for four years now, clinging desperately to the dream of the 2019 popular revolution, when protesters toppled a brutal dictator and inspired sweet hopes of democracy.

But two power-hungry generals still dominate Sudan. And when their relationship disintegrated into violence this weekend, it set off a breathless descent that appeared to be the realization of many people’s worst fears.

Fighting spread to the four corners of the country, where the army and a paramilitary unit known as the Rapid Support Forces battled for control of airfields and military bases. One of the factions even captured and held Egyptian soldiers, along with seven Egyptian warplanes, threatening to suck a powerful neighbor into the fight and raising the specter of a regional conflagration.

The fighting has also spread deep into Darfur, the Spain-size region that for 20 years has been tormented by its own cycle of violence.

For a country that had only recently begun to emerge from international isolation, the chaos is a devastating blow. As Sudan inched toward democracy, the United States had lifted its designation as a state sponsor of terrorism. International aid was promised, and Russian moves to establish a foothold there raised its geostrategic value.

But Sudan’s revolution, like many others, has run aground.

For Omar Farook, it spells the end of a dream.

Like tens of thousands of others, Mr. Farook once risked his life to join the protesters in 2019 whose defiance brought about the ouster of President Omar Hassan al-Bashir, Sudan’s autocratic ruler of three decades.

But this weekend, as Mr. Farook and his wife hunkered down inside their house in the Khartoum suburbs listening to the din of bombs and gunfire, their hopes for democracy evaporated.

“We feel powerless,” he said by phone. “Everyone is worried this will go the way of Yemen or Syria. The ghost of civil war is here.”

More than 83 people have been killed and over 1,126 others injured since April 13, most of them this weekend, the World Health Organization said. The toll includes civilians caught in the crossfire and is expected to rise.

The United Nations World Food Program said that three of its employees had been killed in the western Darfur region and that one of its planes had been destroyed at the airport. The group announced an immediate suspension of all programs in Sudan, where one-third of the country’s 45 million people are in need of food aid.

Sudan was supposed to usher in a momentous new era this month: a return to civilian rule. The army had promised to hand over power last Tuesday, the fourth anniversary of Mr. al-Bashir’s ouster. But that transition depended on the two generals who run the country — the army chief, Gen. Abdel Fattah al-Burhan; and his deputy, the paramilitary commander Lt. Gen. Mohamed Hamdan — keeping their simmering rivalries in check.

Instead they started fighting, dragging Africa’s third-largest country into a chaotic spiral that many fear will end in full-blown civil war.

So far, the world’s attention has been fixed mostly on Khartoum, where uninterrupted internet service has allowed residents to broadcast snippets of the frightening street battles raging outside their doors.

Stunned by the sudden eruption of violence early Saturday, powerful Western and Arab countries on Sunday stepped up their efforts to persuade General al-Burhan and General Hamdan to stop the fighting.

Secretary of State Antony J. Blinken spoke to his counterparts in Saudi Arabia and the United Arab Emirates, uniting in a call for immediate peace talks. The Arab League, of which Sudan is a member, appealed to the warring parties to “stop the bloodshed.”

In an emergency session of the Intergovernmental Authority on Development, a regional bloc that includes Sudan, the presidents of Kenya, South Sudan and Djibouti agreed to make a joint visit to Khartoum, said an official who spoke on the condition of anonymity. No date was set.

Even the U.N. Security Council issued a statement, rare since Russia’s invasion of Ukraine last year, condemning the violence and urging both sides to resume talks.

Sudan’s warring generals did not seem to be listening.

As rival troops exchanged gun and rocket fire on the streets of Sudan, General Hamdan and General al-Burhan engaged in ferocious verbal attacks on television and the internet. Both men claimed to be winning the fight and issued belligerent threats that appeared to leave little room for negotiation.

In one interview, General Hamdan said General al-Burhan “will die like any dog” if he was not brought to justice. And as the violence spread, the Sudanese Army posted a video on Facebook showing soldiers in the eastern city of Qadarif stepping on a photo of General Hamdan.

Another unpredictable factor loomed in a murky episode involving at least 30 detained soldiers from Sudan’s northern neighbor and former colonial ruler, Egypt. General Hamdan’s forces captured the Egyptians and seven warplanes on Saturday at an air base in Meroe, 125 miles north of Khartoum.

Egypt said the soldiers were in Sudan on a training exercise.

But a relative of General Hamdan’s, Izzeldin Elsafi, said by phone that the detained soldiers were mostly pilots and aircraft mechanics who had come to Sudan to carry out airstrikes on behalf of the Sudanese military. He blamed Egypt for airstrikes that hit General Hamdan’s Rapid Support Forces in Port Sudan and Omdurman, across the Nile from Khartoum, on Sunday morning. The planes had taken off from a second Egyptian camp in Sudan, he said.

Those claims could not be verified, but the events made clear the volatility of the conflict and its potential to draw in other states. They also highlighted a critical imbalance between the two clashing military forces: Sudan’s army has warplanes. The Rapid Support Forces do not.

The fighting in Darfur added another combustible element to the conflict. Darfur is home to several rebel groups that could get sucked into the fight, and it has also been a base for Russia’s Wagner private military company, which mines gold there and is allied with General Hamdan.

In Khartoum on Sunday, satellite images showed black smoke filling the sky over the airport, where two large Ilyushin transport planes were on fire. At least four other planes have been burned since Saturday, according to satellite imagery reviewed by The Times.

Many Sudanese said they could scarcely believe what was happening.

Although tensions had been rising between General al-Burhan and General Hamdan for many months, foreign officials pushing for the transition to a civilian government had insisted that it was on track — a source of bitter recrimination now among Sudanese who say the foreigners should have defused the tensions within the military.

And although Sudan has experienced numerous wars in its 67-year history, disastrous as they were, they mostly unfolded in the country’s periphery, hundreds of miles from the capital.

The conflicts led to the secession of South Sudan in 2011; charges of genocide in Darfur at the International Criminal Court; and monumental amounts of death, displacement and suffering, mostly affecting marginalized ethnic groups.

But they rarely affected Khartoum directly.

That changed dramatically this weekend as residents of the capital experienced the kind of trauma that was previously limited to more distant parts of the country. It coincided with the last 10 days of Ramadan, the monthlong period of fasting that is the holiest on the Islamic calendar.

Even after the warring factions announced a three-hour cease-fire in Khartoum on Sunday to allow residents safe passage, the gunfire and explosions did not stop, several people said by phone.

In Kafouri, a wealthy neighborhood north of the Nile, Reem Sinada watched in horror on Saturday as a line of paramilitary battle wagons carrying more than 50 fighters pulled up outside her front door. Her family fled to her brother’s house nearby — but a day later she was cowering again as the windows and doors of her new shelter shuddered from shellfire landing nearby.

“I am overcome with very sad feelings,” Ms. Sinada said by phone. “But, hopefully, we get through this soon.”