Clashes between rival military factions broke out on Wednesday in Sudan's capital, residents said, threatening to shatter a fragile ceasefire designed to allow for the delivery of aid and lay the ground for a more lasting truce.
The ceasefire deal, which is being monitored by Saudi Arabia and the United States as well as the warring parties, comes after five weeks of intensive warfare in the capital Khartoum and outbursts of violence in other areas of the country, including the western region of Darfur.
The fighting pits Sudan's army against the powerful paramilitary Rapid Support Forces (RSF) and has escalated a humanitarian crisis, forcing over 1.3 million people to flee their homes and threatening to destabilize the wider region.
The ceasefire had brought a relative lull in fighting in Khartoum on Tuesday, although little sign of a rapid scale-up in humanitarian relief.
Witnesses reported clashes in several areas of the capital on Wednesday afternoon.
Fighting on the outskirts of Khartoum
West of central Khartoum columns of black smoke could be seen rising into the air, and there was shelling near an army camp in southern Khartoum, they said.
In Bahri, one of the three cities around the confluence of the Blue Nile and White Nile rivers that make up Sudan's greater capital, the sound of clashes and artillery fire could be heard.
Witnesses in Omdurman, the third city, reported that an army fighter plane had been shot down, and videos posted on social media appeared to show the incident. The footage could not immediately be verified.
Earlier, residents reported artillery fire near the Wadi Sayidna military base on the outskirts of Omdurman.
The ceasefire was agreed to on Saturday following talks in Jeddah mediated by Saudi Arabia and the United States. Previous ceasefire announcements have failed to stop the fighting.
Saudi Arabia and the United States late on Tuesday said members of a ceasefire monitoring mechanism that includes representatives of the army and the RSF had undertaken to engage their chains of command about reported truce violations.
The population is terrified
In Nyala, the capital of South Darfur State, days of clashes between the army and the RSF had left most of the main market burned down, two residents said.
"We're in a very difficult situation. We feel emotionally broken and terrified," said resident Malak Ibrahim, adding that her family hadn't had water for the past two weeks.
"We're in a very difficult situation. We feel emotionally broken and terrified."Malak Ibrahim
Activists in Zalingei, the capital of Central Darfur State, said RSF-backed militias had surrounded the city and started looting homes and businesses. Zalingei and West Darfur State capital El Geneina, where hundreds have been killed since last month, both appeared to be cut off from phone networks.
The conflict in Sudan erupted as plans for an internationally backed political transition toward elections under a civilian government were set to be finalized, bringing sustained air strikes and ground fighting to the capital for the first time. Many residents are struggling to survive as they face prolonged water and power cuts, a collapse of health services and widespread lawlessness and looting.
The United Nations human rights chief called the situation in Sudan "heartbreaking" and said there were "very deeply troubling" accounts of sexual violence in Khartoum and Darfur with at least 25 cases reported so far and the real number likely much higher.
Over a million refugees
Aid workers said many of the supplies and staff arriving at Port Sudan on the Red Sea coast have been awaiting security permits and guarantees.
Sudan was facing severe humanitarian pressures even before the conflict broke out on April 15.
More than 1 million people have now been displaced within Sudan and 319,000 have fled Sudan to neighboring countries, some of which are similarly impoverished and have a history of internal conflict, according to the International Organization for Migration. Many have crossed into Chad and Egypt in the last few days, Filippo Grandi, head of the UN refugee agency, said on Wednesday.
"Donor contributions to the refugee response plan remain scarce. We need more resources, urgently, to support countries hosting refugees," he said on Twitter.