Residents of Sudan's capital reported air strikes and clashes over several parts of the capital Khartoum late on Monday as a seven-day ceasefire period agreed by warring military factions began.

News agencies quote witnesses as saying there was some sound of firing heard in Omdurman and Bahri, Khartoum's twin cities, but did not report any major violations of the truce, which was came into effect at 21.45 local time (19:45 GMT).

A series of previous truce announcements were all violated by the warring generals, but the United States and Saudi Arabia - which brokered the deal - had said this one was different because it was "signed by the parties" and will be supported by a "ceasefire monitoring mechanism".

A witness in southern Khartoum told AFP of an air strike, followed by silence, shortly before the ceasefire was to take effect.

Air strikes and gun fire have usually quietened down overnight during the war which has lasted more than five weeks.

Residents of the capital were reported to be anxious for a reprieve to enable them to reach stranded relatives, flee to safety or get access to humanitarian assistance, but said there was little to show fighters were preparing to pause.

"Fighter jets are bombing our neighbourhood," Khartoum resident Mahmoud Salah el-Din told AFP, in the hours before the truce was to take effect.

Conflict in the north African country began on April 15 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.

UN's envoy to Sudan Volker Perthes 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 centre 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, told AFP.

Around 1,000 people have been killed in five weeks of violence that have plunged the already poverty-stricken country deeper into humanitarian crisis. More than one million have been uprooted, including in excess of 250,000 who have fled across Sudan's borders, fuelling concerns for regional stability.