Fighting broke out between the Sudanese Armed Forces and paramilitary Rapid Support Forces on April 15.
Both parties agreed to a ceasefire beginning Tuesday after negotiations mediated by the United States and Saudi Arabia.
Previous bids to pause the conflict failed to take hold, but both sides confirmed they had agreed to the three-day halt.
UN Secretary-General Antonio Guterres described the violence and chaos in Sudan as "heart-breaking."
United Nations
A US-brokered ceasefire in Sudan appears to be partially holding but there is no sign the warring parties are ready to seriously negotiate, the UN special envoy on Sudan said on Tuesday.
This suggested "that both think that securing a military victory over the other is possible," envoy Volker Perthes told the UN Security Council.
Sporadic gunfire rang out in parts of the Sudanese capital Khartoum on Tuesday despite a US-brokered agreement between the warring generals to cease fire for 72 hours to pave the way for talks on a more lasting truce.
Fighting broke out between the Sudanese Armed Forces (SAF) and paramilitary Rapid Support Forces (RSF) on April 15.
Both parties agreed to a ceasefire beginning Tuesday after negotiations mediated by the United States and Saudi Arabia.
"It seems to be holding in some parts so far. However, we also hear continuing reports of fighting and movement of troops," said Perthes, who spoke via video from Port Sudan.
Previous bids to pause the conflict failed to take hold, but both sides confirmed they had agreed to the three-day halt.
‘Heart-breaking’
UN Secretary-General Antonio Guterres described the violence and chaos in Sudan as "heart-breaking."
Guterres on Monday warned that Sudan was on "the edge of the abyss" and that the violence "could engulf the whole region and beyond".
The power struggle puts Sudan's future at risk and could cause suffering for years and set back development for decades, Guterres said.
The United Nations has moved hundreds of staff and family members to Port Sudan from Khartoum.
UN hub in Port Sudan
The UN plans to establish a hub in Port Sudan to continue working in the country where, even before the violence broke out, nearly 16 million people — one-third of the population — needed humanitarian aid.
Ten days of heavy fighting, including air strikes and artillery barrages, have killed hundreds of people, many of them civilians, and left some neighbourhoods of greater Khartoum in ruins.
But in other areas there has been a reduction in the intensity of fighting since foreign governments scrambled road convoys, aircraft and ships to get their nationals out since the weekend, witnesses said.
Unconfirmed video posted on social media showed bewildered civilians walking down one street in Khartoum North where virtually every building was bombed out and smoke was still rising from the scorched ruins.
Unable to flee
Millions of Sudanese are unable to flee the country, which has a history of military coups. They are trying to survive acute shortages of water, food, medicine and fuel as well as power and internet blackouts.
The capital Khartoum, a city of five million, has endured "more than a week of unspeakable destruction", Norway's ambassador Endre Stiansen wrote on Twitter after his evacuation.
A UN convoy carrying 700 people on Monday completed an arduous 850-kilometre road trip to Port Sudan on the Red Sea coast from the capital.