A 7-day cease-fire agreed to by Sudan's warring factions began late on Monday.
Witnesses cited by several news agencies reported airstrikes and clashes shortly after the latest in a series of truces during the five-week conflict came into effect.
And in the hours leading up to the truce, Sudan's armed forces and the powerful paramilitary Rapid Support Forces (RSF) continued to face off in the capital, Khartoum.
What are the details of the cease-fire in Sudan
The cease-fire, brokered by Saudi Arabia and the US, is the first to have been physically signed by representatives of the warring parties. The mediating states thus have hope that unlike previous cease-fire agreements since the fighting started on April 15, this one will be upheld.
Shortly before the cease-fire took effect, RSF commander Mohamed Hamdan Dagalo thanked Saudi Arabia and the US for brokering the agreement but insisted that his forces would continue until victory.
"We will not retreat until we end this coup," he said.
What is different about this cease-fire?
Following talks held in Jeddah, the representatives of the Sudanese army and the Rapid Support Forces officially agreed upon a seven-day cease-fire.
The possibility of extending the truce will be considered if both parties mutually agree.
The US-Saudi statement acknowledged, "it is widely known that the parties have previously declared cease-fires that were not upheld."
In contrast, the recent agreement reached in Jeddah will be backed by a cease-fire monitoring mechanism supported by the US, Saudi Arabia, and the international community.
Hours before the cease-fire was scheduled to come into effect, RSF leader Mohamad Hamdan Dagalo released an audio recording on Twitter, thanking both Saudi Arabia and the US for their mediation efforts.
"We will not retreat until we end this coup," said Dagalo, in reference to the armed forces' attacks against his RSF. He vowed to hold to account "those who have committed crimes against the people of Sudan, and return our country to the path of democracy."
UN warns of conflict 'ethnicization'
Residents of the capital woke up yet again to gunfire and explosions on Monday, with airstrikes reported in Khartoum, Omdurman and Bahri.
"Fighting and troop movements have continued even today, despite a commitment by both sides not to pursue military advantage before the cease-fire takes effect," Volker Perthes, the UN's envoy to Sudan, told the Security Council on Monday.
The army has consistently relied on airstrikes in an attempt to expel RSF forces from strategic positions on the ground in Khartoum's neighborhoods, to no avail. The paramilitary forces have occupied civilian buildings in the capital since the start of the fighting.
"Fighter jets are bombing our neighborhood," Khartoum resident Mahmoud Salah el-Din told the French AFP news agency. "We have seen no sign that the Rapid Support Forces are preparing to withdraw from the streets."
"The situation is horrible. The planes are bombing us on every side and from the strength of the vibration of the house doors, we feel like we'll die today," Salma Abdallah, a resident of Al Riyadh neighborhood in Khartoum, told the Reuters news agency.
During the UN Security Council briefing, Volker warned of the growing "ethnicization" of the conflict.
"In parts of the country, fighting between the two armies or the two armed formations has sharpened into communal tensions, or triggered conflict between communities," he said.
rmt/wd (AFP, Reuters)