Rival government factions in Sudan have rejected calls for a ceasefire and intensified their battle for control of the vast and strategically important country as diplomatic efforts to end the conflict gather momentum. At least 185 people have been killed and more than 1,800 injured, UN envoy Volker Perthes said as clashes have spread since Saturday, when violence erupted between army units loyal to Gen Abdel Fattah al-Burhan, the head of Sudan’s transitional governing Sovereign Council, and the paramilitary Rapid Support Forces (RSF), led by Gen Mohamed Hamdan Dagalo, known as Hemedti, who is deputy head of the council. Fighting in Khartoum has centred on key sites such as the international airport, presidential palace and the army headquarters, where Burhan is thought to be based. Josep Borrell, the EU foreign policy chief, said that the EU ambassador in Khartoum had been assaulted at his residency. Borrell did not say if the ambassador, Irish diplomat Aidan O’Hara, had been badly injured, but called the attack “a gross violation of the Vienna Convention”, which is supposed to guarantee the protection of diplomatic premises. US national security council spokesperson, John Kirby, said that the Biden administration had been in contact with both sides urging an immediate unconditional ceasefire, but the call went unheeded. Kirby said the US was not, for the time being, planning an evacuation. Burhan raised the stakes in the violence still further on Monday, ordering the dissolution of the RSF, which he called a “rebellious group”. For his part, Dagalo called Burhan “a radical Islamist who is bombing civilians from the air”. Military jets flew low over the capital through much of Monday as repeated bouts of firing and shelling continued there and in Omdurman, Khartoum’s sister city across the Nile. Witnesses have reported dozens of bodies in one central neighbourhood of the capital, and hundreds of students remain trapped by the fighting in schools. Hospitals have been particularly affected, with essential supplies badly disrupted by the fighting. Hundreds of patients have been evacuated, while medical staff work to move others from intensive care or dialysis units to places of safety. “We had to move them to the isolation centres along with 70 doctors and nurses, all have been trapped here with no oxygen for the chest patients and that’s really dangerous … The oxygen we have is from the time of the pandemic and it’s limited,” one nurse said. A shell hit one Khartoum teaching hospital on Monday morning, injuring several patients and relatives. Another hospital has appealed for fuel to keep generators running. A dentist taking her sick father for treatment at another facility was killed, according to activists in the UK. A doctor who spoke to the Guardian from the basement of the Khartoum teaching hospital described heavy shelling and orders from army soldiers to leave the premises. “We are basically in the crossfire between the RSF and the army. They are firing at each other from their positions and we are in between.” The doctor, who asked to remain anonymous, described an acute need for food and drinking water. Dr Sara Ibrahim Abdelgalil, a UK-based Sudanese democracy activist who is in touch with many health professionals in Khartoum, said: “It is very bad. The real issue is that the armed conflict is inside residential areas. We don’t know how many casualties. Neither the RSF nor the army are promising protection of health workers, patients, humanitarians, the Red Crescent or ambulances and there’s no suggestion that they will in the future.” In some parts of the city, informal neighbourhood committees have taken over the distribution of painkillers and rehydration salts to ill children who cannot be taken for treatment. “Three families have contacted me to tell me about sick kids who they can’t get to medical attention. They can’t even get paracetamol to bring the temperature down,” Abdelgalil said. With replacements unable to risk the streets of the city, many staff have been on duty since Friday and are exhausted. With water and power cut across large parts of the capital, long queues formed at bakeries as some residents ventured out to buy food. There has been no police presence on the streets of Khartoum since Saturday, and witnesses reported cases of looting. “We’re scared our store will be looted because there’s no sense of security,” 33-year-old shopkeeper Abdalsalam Yassin told Reuters. UN chief António Guterres urged a return to calm, saying an already precarious humanitarian situation was now catastrophic. Aid workers in remote parts of Sudan also reported tensions or violence. One based in on the eastern border with Ethiopia described the regular army overwhelming a small RSF contingent and seizing their base amid sporadic shooting. Officials also reported fighting in the east, including the provinces of Kassala and El Gadaref. There were also reports of clashes at Merowe, 185 miles (300km) north of Khartoum, and in many parts of the Darfur region. The more heavily armed regular military loyal to Burhan appeared to have the upper hand in the fighting over the weekend, but both sides are making claims and counterclaims that are impossible to verify. “The army seem to be doing well but the RSF have lots of men, weapons and vehicles so could hold out for a really extended time and that’s the scary thought. We just don’t know,” said one aid worker based in El Gedaref, south-east of Khartoum. The conflict threatens to plunge one of Africa’s biggest and most strategically important countries into chaos. Analysts say only pressure from “heavyweight” intermediaries will have a chance of ending the fighting. In Washington, Kirby said the administration was trying to coordinate with the African Union, the Arab League, and the regional organisation, the Intergovernmental Authority on Development, “about how we collectively press the parties to end the fighting”. “We’ve been very clear what we want to see happen here, which is a ceasefire, a return to an approach that is supportive of the democratic institutions and the elected civilian leadership,” he said. In a speech broadcast by Egyptian state television late on Monday, Egypt president Abdel Fattah al-Sisi said he was in regular contact with the army and RSF to “encourage them to accept a ceasefire and spare the blood of the Sudanese people”. The African Union’s top council has called for an immediate ceasefire “without conditions”, while Arab states with stakes in Sudan – Qatar, Saudi Arabia and the United Arab Emirates – made similar appeals. The UN security council was to discuss the crisis on Monday. Neither of the factions fighting for control of Sudan and its precious resources has shown any willingness to compromise. Burhan’s followers have called for the dismantling of the RSF, while Dagalo told the satellite news network Al Arabiya that he had ruled out negotiation and called on Burhan to surrender. The roots of the conflict lie in the divide-and-rule strategy pursued by the veteran Islamist autocrat Omar al-Bashir, who took power in 1989. The RSF was drawn from the feared Janjaweed militia accused of genocide in Darfur and acted as a counterweight to the regular army, whose loyalty Bashir doubted. The two forces joined to oust Bashir in 2019 after months of mass popular protests, but relations between them remained tense. Many analysts and diplomats in Khartoum predicted a violent contest after a military coup in October 2021 that derailed a gradual transition to civilian rule. Sudan is in a deep economic crisis, with soaring inflation and massive unemployment. Khalid Omar, a spokesperson for the pro-democracy bloc that negotiated with the generals in recent months, warned that the conflict could lead to war and the country’s collapse.