Witnesses in the Sudanese capital reported clashes and air strikes minutes after a one-week ceasefire was to have come into force to let through life-saving humanitarian assistance.
They reported combat in north Khartoum, and air strikes in the east of the capital shortly after 9:45 pm (1945 GMT) Monday night when the truce was to take effect, with the smell of smoke still lingering after gunfire and explosions rocked the city throughout the day.
The ongoing fighting dampened hopes for a pause to allow in humanitarian aid or let residents flee.
A series of previous truce deals were all violated.
"Beyond official announcements, Sudan is still pounded and bombarded, with millions of civilian lives at risk," Karl Schembri of the Norwegian Refugee Council wrote on Twitter.
"We've had over a month of broken promises and empty words while humanitarian colleagues were killed, together with children and others and hospitals destroyed."
Since April 15, fighting between the army, led by Sudan's de facto leader Abdel Fattah al-Burhan, and the paramilitary Rapid Support Forces commanded by Burhan's former deputy Mohamed Hamdan Daglo, has left about 1,000 people dead and forced more than a million to flee their homes.
Earlier on Monday, residents of the capital --anxious for a reprieve to enable them to reach stranded relatives, flee to safety or get access to humanitarian assistance-- said there was little to show fighters were preparing to pause, reporting air strikes and anti-aircraft fire for the 37th consecutive day.
"Fighter jets are bombing our neighborhood," Khartoum resident Mahmoud Salah el-Din told AFP, in the hours before the truce was to take effect.
While no previous truce has held, the United States and Saudi Arabia --which brokered the deal-- said this one was different because it was "signed by the parties" and would be supported by a "ceasefire monitoring mechanism".
Air strikes and gunfire have usually quietened down overnight during the war, which has now lasted more than five weeks.
According to the seven-page agreement released by the United States, warring sides were to use the two days before it took effect Monday night to "inform their respective forces" about it and "instruct them to comply".
But Volker Perthes, the UN's envoy to Sudan, told the United Nations Security Council that "fighting and troop movements have continued even today, despite a commitment by both sides not to pursue military advantage before the ceasefire takes effect".
While government forces control the skies, they have few men on the ground in the center of Khartoum, where RSF are on the streets.
"We have seen no sign that the Rapid Support Forces are preparing to withdraw from the streets," said Salah el-Din, the Khartoum resident.
We are all hungry
Hours before the truce was to start, Daglo released a voice message on social media addressing reported violations by his forces --including rampant looting, targeting of civilians and attacks on churches-- all of which he blamed on "coup plotters" in the army.
To his fighters, he said: "It is either victory or martyrdom, and victory will be ours".
At the Security Council, Sudan's representative, loyal to Burhan, blamed the RSF for similar violations.
Despite the previous breached truces, civilians clung to hope that the new ceasefire would hold, allowing desperately needed aid to bolster dwindling supplies of food, medicine and other essentials.
"We are all hungry, the children, the elderly, everyone is suffering from this war. We have no more water," Khartoum resident Souad al-Fateh told AFP, pleading for both sides to "find an agreement".
The violence has plunged the already poverty-stricken country deeper into crisis, with more than half the population, 25 million people, in need of humanitarian aid, according to the UN.
For Thuraya Mohammed in southern Khartoum, the truce would be a chance to escape, because "Khartoum is no longer a place fit for life. Everything has been destroyed."
Late Monday, the doctors' union announced the closure of "the only hospital that had remained servicing" two districts east of the capital, after days of RSF troops "assaulting and intimidating patients, families and medical staff" inside the hospital, in addition to the army "personally threatening" hospital staff.
Targeted by both camps and suffering a severe shortage of supplies, medics have repeatedly warned that the health care system --already fragile before the war-- is on the verge of collapse in Khartoum and elsewhere, particularly the western region of Darfur.