- But there have been some breaches of the truce in Khartoum, and across the River Nile in Bahri and Omdurman.
- The military carried out air strikes minutes after the ceasefire came into force on Monday evening.
The latest ceasefire aimed at ending the devastating conflict in Sudan appears to be largely holding in the capital and two adjacent cities.
For the first time in more than five weeks there appears to be relative peace, residents say.
But there have been some breaches of the truce in Khartoum, and across the River Nile in Bahri and Omdurman.
The military carried out air strikes minutes after the ceasefire came into force on Monday evening.
The air strikes, targeting the paramilitary Rapid Support Forces (RSF), have since stopped.
However, sporadic artillery fire could still be heard in Khartoum, residents told AFP news agency.
The RSF controls much of Khartoum and the two other cities that make up Sudan's greater capital.
The situation is also relatively calm in El Geneina and Nyala, two cities in the Darfur region which have also been badly affected by the conflict, AFP quotes witnesses as saying.
The violence began on 15 April, triggered by a power struggle between the leaders of the regular army and the RSF.
The US and Saudi Arabia have been brokering talks aimed at ending the conflict, which has forced more than one million people from their homes and has led to a breakdown in health services.
Previous ceasefires collapsed, but the US said the latest one was different as it included a monitoring mechanism.
US secretary of state Antony Blinken said the monitoring would be "remote", but did not give details.
"If the ceasefire is violated, we'll know, and we will hold violators accountable through our sanctions and other tools at our disposal," he added in a video message to the Sudanese people.
RSF commander Gen Mohamed Hamdan Dagalo - better known as Hemedti - issued a belligerent message just hours before the agreement was due to become effective.
He was recorded in an audio message saying his troops would not retreat "until we end this coup".
Khartoum resident Moe Faddoul told the BBC that minutes into the ceasefire there were two heavy air strikes west of the city, where the military's main airbase is.
"The house shook where I'm staying," he said.
There were also skirmishes, but the fighting had since stopped, Mr Faddoul added.
He described the city as "almost a ghost town".
Most residents had fled, no cars were on roads and only a few people were walking to look for basic necessities, Mr Faddoul said.
The army and RSF agreed to the ceasefire lasting for seven days, raising hopes that aid workers would be able to deliver much-needed food and medical supplies.
The US has announced $245m (£197m) in humanitarian aid to Sudan and neighbouring states, which are bearing the brunt of the refugee crisis triggered by the conflict.