"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.
There was no immediate comment from the army.
Before Friday, two declared 24-hour ceasefires had failed to take hold.
Amid the ongoing fighting, the United Nations (UN) continued to appeal to the RSF and Sudanese Army to strike a deal.
UN Secretary-General Antonio Guterres on Thursday called for a three-day ceasefire in Sudan to allow trapped civilians to flee.
"As an immediate priority, I appeal for a ceasefire to take place for at least three days, marking the Eid al-Fitr celebrations, to allow civilians trapped in conflict zones to escape and to seek medical treatment, food and other essential supplies," he told reporters at the UN headquarters in New York.
The UN chief said hundreds of people have been killed and injured in the fighting, and humanitarian operations are virtually impossible.
UN agencies on Thursday also expressed concern over the impact of fighting on civilians in Sudan, where the humanitarian situation was already dire.
The World Health Organization reported more than 330 people killed during six days of fighting in the capital city of Khartoum and several other states, including Darfur. Another 3,200 people were injured.
The UN children’s fund (UNICEF) said at least nine children were reportedly killed in the fighting and more than 50 children were injured.
UNICEF Executive Director Catherine Russell said the perilous security situation across Sudan makes it very difficult to collect and verify information. But UNICEF is certain that while the fighting continues, children will continue to pay the price.
The UN Office for the Coordination of Humanitarian Affairs (OCHA) said people have been unable to safely leave their homes to buy food and other essentials for days now. Humanitarian pauses must be ensured to enable the safe passage of civilians so that they can seek medical care and access basic provisions.
The humanitarian response in Sudan is severely hampered, said OCHA.
Meanwhile, the World Food Programme warns that the fighting in Sudan could plunge millions more into hunger.
Fighting between the Sudanese Armed Forces and the RSF broke out on Saturday, forcing civilians to flee and seek shelter from the hostilities. Hundreds of people have been killed and thousands injured.