The RSF however denied the army had advanced.
The Sudanese army has claimed its first major advance in 10 months of war, regaining control of part of the city of Omdurman from the Rapid Support Forces (RSF).
The army said late on Friday it had succeeded in connecting its two main bases in the city, prompting celebrations among soldiers and local residents.
The RSF however denied the army had advanced.
"The army has turned to propaganda as it is on the verge of defeat," RSF media office said in a statement.
The RSF has been fighting the army for control of Sudan since April in a war that has killed thousands, displaced almost 8 million, and sparked warnings of famine.
Soon after war broke out, the RSF took control of most of the capital Khartoum, its sister cities Bahri and Omdurman, and most of the territory in the western Kordofan and Darfur regions.
The army held on to most of its bases in the capital but had not made major advances until the start of the year, when residents reported it was making greater use of drones.
That appeared to help the army push out of its strongholds around bases in the north and south of the city and create a band of control across the length of the capital.
The RSF maintains control of areas in the east of Omdurman as well as the wide Ombada district that connects the capital to the western regions, and residents say it has snipers stationed along key routes.
Despite a two-week internet blackout, images emerged from the city showing civilians and soldiers celebrating.
Residents of Omdurman, Khartoum and other cities say the RSF has forced them out of their homes, looted belongings, and raped women. The force is accused of crimes against humanity, war crimes, and ethnic cleansing in West Darfur state by the US.
The army, which has carried a broad campaign of air strikes, is also accused of war crimes. The army and the RSF deny the accusations.
The RSF says rogue actors will be brought to justice.