However, Burhan said he was open for mediation but there will be no "direct" talks with the paramilitaries.

In a statement earlier, Sudan's military ruled out negotiations with a the Rapid Support Forces (RSF) force on Thursday, saying it would only accept its surrender as the two sides continued to battle in central Khartoum and other parts of the country.

The military's statement raised the likelihood of a renewed surge in the nearly week-long violence that has pushed Sudan's population to the breaking point. Alarm has grown that the country's medical system was on the verge of collapse, with many hospitals forced to shut down and others running out of supplies.

The 24-hour cease-fire, declared Wednesday evening, had brought only marginal calm to parts of the capital of Khartoum, but many residents took advantage to flee the homes where they have been trapped for days. “Massive numbers” of people, mostly women and children, were leaving in search of safer areas, said Atiya Abdulla Atiya, secretary of the Doctors’ Syndicate.

Hours before the truce was set to end, the military said in a statement that it would not negotiate with its rival, the Rapid Support Forces, over an end to the crisis and would only discuss terms of its surrender. “There would be no armed forces outside (of) the military system,” it said.

If the truce collapses completely, it would mark the second failure by the international community to push Sudan's two top generals — army chief Gen. Abdel Fattah Burhan and RSF commander Gen. Mohammed Hamdan Dagalo — to halt their battle for control of the country.

A similar truce Tuesday, which came after U.S. Secretary of State Antony Blinken spoke by phone with both generals, collapsed almost immediately.

At least 330 people have been killed and 3,300 wounded in the fighting since it began Saturday, the U.N.’s World Health Organization said, but the toll is likely higher because many bodies lie uncollected in the streets.

Through the night and the day Thursday, gunfire could be heard almost constantly across Khartoum. Residents reported the heaviest fighting around the main military headquarters in central Khartoum and at the nearby airport. Military warplanes struck RSF positions at the airport and in the neighboring city of Omdurman, residents said.

The military said its warplanes Thursday also struck a convoy of RSF vehicles heading into the capital, though the claim could not be independently confirmed.

Khartoum residents have been desperate for respite after days of being trapped in their homes, their food and water running out. “Sounds of gunfire and air bombing are still heard,” Atiya told The Associated Press said. “It is escalating, and the situation is deteriorating rapidly.”

The truce has not been firm enough to deliver supplies and relief to Sudan’s overwhelmed hospitals, Atiya said. Hospitals in Khartoum are running dangerously low on medical supplies, often operating without power and clean water. Around 70 percent of hospitals near the clash sites throughout the country are out of service, the Sudanese Doctors Syndicate said Thursday. At least nine hospitals were bombed, it said.

Airstrikes on Thursday afternoon hit medical facilities in Obeid, the capital of North Kordofan province southwest of Khartoum, and likely caused dozens of casualties, Atiya said. Clashes have intensified in the city, driving hundreds of people from their homes to take shelter in nearby camps for people displaced from previous conflicts, he said.

The fighting has been disastrous for a country where the United Nations says around a third of the population — some 16 million people — are in need of humanitarian aid. The U.N. children’s agency UNICEF warned that critical care has been disrupted for 50,000 severely acutely malnourished children, who need round-the-clock treatment.

Save the Children said power outages across the country have destroyed cold chain storage facilities for lifesaving vaccines, as well as the national stock of insulin and several antibiotics. Millions of children, the aid group said, are now at risk of disease and further health complications. It said 12 percent of the country’s 22 million children are suffering from malnutrition and are vulnerable to other diseases.

The conflict has raised fears of a spillover from the strategically located nation to its African neighbors.

Sudan’s fighting has also caused up to 20,000 Sudanese to seek refuge in eastern Chad, the U.N. said Thursday. At least 320 Sudanese soldiers fled to Chad, where they were disarmed, said Daoud Yaya Brahim, Chad’s defense minister. The troops were apparently fleeing from Darfur, where the RSF is the most powerful armed force.

“Chad is for the moment trying to remain neutral … (but) Chad will be forced to pick sides if Sudan continues its descent into civil war,” said Benjamin Hunger, Africa analyst for Verisk Maplecroft, a risk assessment firm.