Sudan's paramilitary Rapid Support Forces (RSF) had agreed to a 72-hour truce on humanitarian grounds from 6 am (0400 GMT) on Friday, to coincide with the Muslim holiday of Eid al-Fitr.
The capital, Khartoum, was rocked by bombing and shelling earlier on Friday. There was no immediate comment from the army and its chief, General Abdel Fattah al-Burhan, did not mention a ceasefire in a pre-recorded speech posted on the army's Facebook page, reports AFP.
"The truce coincides with the blessed Eid al-Fitr ... to open humanitarian corridors to evacuate citizens and give them the opportunity to greet their families," the RSF said in a statement.
Fighting between the RSF and Sudan's army erupted on Saturday, derailing an internationally backed plan for a transition to a civilian democracy four years after the fall of Islamist autocrat Omar al-Bashir to mass protests and two years after a military coup.
The RSF said it had to act in "self-defense" to repel what it described as a coup attempt, adding that it is committed to a "complete ceasefire" during the armistice period.
At least 350 people have been killed in the power struggle between two previously allied leaders of the ruling military junta, army chief Burhan and RSF leader General Mohamed Hamdan Dagalo.
Bd-pratidin English/Golam Rosul