KHARTOUM, Sudan (AP) — 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 56 civilians were reported killed, including three Sudanese employees of the UN food agency. The Sudan Doctors’ Syndicate said it believed there were dozens of additional deaths among the rival forces. It said close to 600 people were wounded, including civilians and fighters.

The clashes are part of a power struggle between General Abdel-Fattah Burhan, the commander of the armed forces, and General 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.

In Khartoum and Omdurman, fighting was reported around the military headquarters, Khartoum International Airport and state television headquarters. A senior military official said RSF fighters clashed with troops at military headquarters early Sunday and that a fire broke out at a facility for ground troops.

“The battles have not stopped,” said prominent rights advocate Tahani Abass who lives near the military headquarters. “They are shooting against each other in the streets. 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 US Secretary of State, the UN 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 UN Security Council, at odds over other crises around the world, called for an immediate end of the hostilities and a return to dialogue.

Arab states with stakes in Sudan — Qatar, Egypt, Saudi Arabia and the United Arab Emirates — made similar appeals.

US 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.

At the Vatican, Pope Francis said he was following “with worry” the events unfolding in Sudan. “I am close to the Sudanese people … and I invite prayers so that arms are laid down and dialogue prevails, to resume together the path of peace and harmony,” the pontiff said in remarks Sunday to the public in St Peter’s Square.

The World Food Program said it temporarily suspended operations in Sudan after three agency employees were killed in the clashes 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 UN.

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.

The country has borders with six African nations and a strategic coastline on the Red Sea. A decade-old civil conflict resulted in the secession of South Sudan in 2011.