KHARTOUM, Sudan — The Sudanese military and a powerful paramilitary group battled for control of the chaos-stricken nation for a second day Sunday , signaling they were unwilling to end hostilities despite mounting diplomatic pressure to cease fire.

Heavy fighting involving armored vehicles, truck-mounted machine guns and war planes raged Sunday in the capital of Khartoum, the adjoining city of Omdurman and in flashpoints across the country. The rival forces are believed to have tens of thousands of fighters each in the capital alone.

At least five civilians were killed and 78 wounded Sunday, bringing the two-day toll to 61 dead and more than 670 wounded, said the Sudan Doctors' Syndicate. The group said it believes there were dozens of additional deaths among the rival forces.

The clashes are part of a power struggle between Gen. Abdel-Fattah Burhan, the commander of the armed forces, and Gen. Mohammed Hamdan Dagalo, the head of the Rapid Support Forces group. The two generals are former allies who jointly orchestrated an October 2021 military coup that derailed Sudan's short-lived transition to democracy.

In recent months, internationally backed negotiations revived hopes for such a transition, but growing tensions between Burhan and Dagalo eventually delayed a deal with political parties .

Volker Perthes, the U.N. envoy for Sudan, said that both Burhan and Dagalo agreed to a three-hour humanitarian pause in fighting in the late afternoon Sunday, but violence continued to engulf the capital.

As night fell, residents reported heavy explosions and continued gunfire. Some said thick flames could be seen in the city center where both the army and the RSF have military facilities and camps. The clashes come as most Sudanese are preparing to celebrate the holiday that marks the end of the holy month of Ramadan, when Muslims traditionally fast from sunrise to sunset.

Fighting raged around the military’s headquarters throughout the day. “Heavy explosions and gunfire around the clock,” said Amany Sayed, a 38-year-old Khartoum resident. “The battles here (in the capital) never stopped.”

In Khartoum and Omdurman, fighting was also reported around Khartoum International Airport and state television headquarters. A senior military official said clashes with RSF fighters began earlier in the day around military headquarters.

“They are shooting against each other in the streets," said prominent rights advocate Tahani Abass who lives near the military headquarters. "It’s an all-out war in residential areas.”

Abass said her family spent the night huddling on the ground floor of their home. “No one was able to sleep and the kids were crying and screaming with every explosion,” she said. Sounds of gunfire were heard while she was speaking to The Associated Press.

The military and the RSF both claimed to be in control of strategic locations in Khartoum and elsewhere in the county. Their claims couldn’t be independently verified.

Both sides signaled that they were unwilling to negotiate.

Burhan's military called for dismantling the RSF, which it labeled a “rebellious militia.” Dagalo told the satellite news network Al Arabyia that he ruled out negotiation and called on Burhan to surrender.

Meanwhile, diplomatic pressure appeared to be mounting.

Top diplomats, including the U.S. Secretary of State, the U.N. secretary-general, the EU foreign policy chief, the head of the Arab League and the head of the African Union Commission urged the sides to stop fighting. Members of the U.N. Security Council, at odds over other crises around the world, called for an immediate end of the hostilities and a return to dialogue.

The African Union’s top council called Sunday for an immediate cease-fire "without conditions.” It also asked the AU Commission Chairman Moussa Faki Mahamat to “immediately travel to Sudan to engage the parties towards a cease-fire.”

Arab states with stakes in Sudan — Qatar, Egypt, Saudi Arabia and the United Arab Emirates — made similar appeals. Saudi Foreign Minister Prince Farhan bin Faisal spoke by phone with Sudan’s rival generals and urged them to stop “all kinds of military escalation,” Saudi state TV reported.

U.S. Secretary of State Antony Blinken said he consulted with the foreign ministers of Saudi Arabia and the United Arab Emirates. “We agreed it was essential for the parties to immediately end hostilities without pre-condition,” he said in a statement early Sunday.

On Sunday, the World Food Program said it temporarily suspended operations in Sudan after three agency employees were killed in clashes the previous day and an aircraft used by the WFP was damaged.

“We cannot do our lifesaving work if the safety and security of our teams and partners is not guaranteed,” said Cindy McCain, the executive director of the agency. About 16 million people, or one-third of Sudan's population, require humanitarian assistance, according to the U.N.

The rival forces were fighting in several locations across Sudan, including the western Darfur region where tens of thousands of people live in camps for displaced people after years of genocidal civil war.

The three WFP employees were killed in clashes in the town of Kebkabiya in the province of North Darfur. Two agency employees were wounded.

Dozens of people were also killed and wounded since Saturday at a camp for displaced people in North Darfur, said Adam Regal, a spokesman for a Darfur charity.

In Nyala, the capital of South Darfur province, the two sides fought for control of the city's airport, said a military official who spoke on condition of anonymity because he was not authorized to brief media.

The official said fighting also spread to the eastern region, including the provinces of Kassala and al-Qadarif on the borders with Ethiopia and Eritrea. He said battles centered around RSF and army bases.

The recent tensions stem from disagreement over how the RSF, headed by Dagalo, should be integrated into the armed forces and what authority should oversee the process. The merger is a key condition of Sudan’s unsigned transition agreement with political groups.

Pro-democracy activists have blamed Burhan and Dagalo for abuses against protesters across the county over the past four years, including the deadly break-up of a protest camp outside the military’s headquarters in Khartoum in June 2019 that killed over 120 protesters. Many groups have repeatedly called for holding them accountable. The RSF has long been accused of atrocities linked to the Darfur conflict.

Sudan, a country at the crossroads of the Middle East and Sub-Saharan Africa, is known for its history of military coups and civil conflicts since it gained independence in 1950s. A decade-old civil conflict resulted in the secession of South Sudan in 2011.

U.N. Secretary-General Antonio Guterres called for those responsible for the death of civilians, including three employees with the U.N. food agency, to be held accountable, according to his spokesman, Stéphane Dujarric.

The U.N. Security Council will discuss the crisis in Sudan on Monday, said Fedor Strzhizhovskiy, the spokesman for the U.N. mission of Russia, which holds the council's presidency this month.

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Magdy reported from Cairo.

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Associated Press writer Frances D’Emilio in Rome contributed.