A truce signed on Monday by the two fighting parties - Sudan's army and a paramilitary group called the Rapid Support Forces - aimed to secure safe passage for humanitarian aid and lead to wider talks sponsored by the United States and Saudi Arabia.
On Saturday, witnesses said Khartoum was calmer, although sporadic clashes were reported overnight.
Gulf broadcaster Al-Arabiya reported some clashes in northwestern Khartoum and southern Omdurman, a city neighbouring the capital.
In a statement on Saturday, the RSF accused the army of violating the ceasefire and destroying the country's mint in an air strike.
The army had accused the RSF on Friday of targeting the mint.
The army said meanwhile that its call on Friday for army reservists was a partial mobilisation and constitutional measure, adding the army expected large numbers to respond to the call.
The conflict, which erupted on April 15, has killed at least 730 civilians and caused 1.3 million Sudanese to leave their homes, fleeing either abroad or to safer parts of the country.
Those who remain in Khartoum are struggling with failures of services such as electricity, water and phone networks.
Looters have ransacked homes, mostly in well-off neighbourhoods.
On Saturday, Sudanese police said they were expanding deployment and also called in able retired officers to help.
"Our neighbourhood has become a war zone," said 52-year-old Ahmed Salih, a resident of the city.
"Services have collapsed and chaos has spread in Khartoum.
"No one is bothered to help the Sudanese people, neither the government nor internationally.
"We are humans - where is the humanity?" he said.
Aid agencies say despite the truce they have struggled to get the bureaucratic and security guarantees to transport aid and staff in safer parts of the country to Khartoum and other hot zones.
Warehouses have been looted.
Fighting has also expanded into the fragile Darfur region, most impacting the western city of El Geneina, which has seen an onslaught of militia attacks that have destroyed its infrastructure and killed hundreds.
The governmental Combating Violence Against Women and Children Unit said late on Friday it had received reports of 25 cases of rape of women and girls in Darfur and 24 reports of rape in Khartoum since the conflict erupted.
It said that victims had described 43 of the men as wearing RSF uniforms and either riding vehicles with RSF licenses or located in RSF-controlled areas.
"The unit expresses its grave concern over reports of gang rape, kidnapping ... and reports of women and girls facing sexual assault as they go out to seek food," it said.
The RSF has denied reports its soldiers are engaged in sexual assaults or looting.
Reuters could not independently verify the unit's allegations.
