It came a day after the paramilitary Rapid Support Forces set up a base in Wad Madani, where their offensive has sent thousands fleeing Sudan's second city and former aid hub, many of them already displaced.
The paramilitary Rapid Support Forces (RSF) "took control of Rufaa," 40 kilometers (25 miles) north of Wad Madani, the witnesses told AFP.
They said the RSF took over "the army headquarters, the police office, and the hospital after a clash that lasted for one hour" in the town.
Since fighting broke out on April 15 between army chief Abdel Fattah al-Burhan and his former deputy, RSF commander Mohamed Hamdan Daglo, the city of Wad Madani, 180 kilometers (110 miles) south of Khartoum, became a haven for thousands of displaced people during the conflict.
The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) said in a statement that the city's population had reached 700,000, after more than half a million people took shelter there, among them 270,000 who "need humanitarian assistance."
The RSF announced on X, formerly Twitter, on Monday that they "seized control of the SAF (army) First Infantry Division in Wad Madani."
It said its "operation included the liberation of the central reserve camp and the strategic Hantoob Bridge from the eastern side."
FILE - Displaced people fleeing from Wad Madani in Sudan's Jazira state arrive in Gedaref in the country's east on December 18, 2023.
On Sunday, the army reported in a statement that the RSF attempted to capture Wad Madani.
"The security situation in Al-Jazira state has stabilised," the army said, adding, "we call on our people not to leave their homes."
The RSF had on Sunday "set up bases in the Al-Malikiyah neighbourhood, east of the city of Wad Madani," an AFP correspondent said.
The Norwegian Refugee Committee and the Intergovernmental Authority on Development (IGAD) East African bloc expressed concern over the spiraling violence in Al-Jazira state.
The American embassy warned on Sunday in a statement that "the continued advance of the Rapid Support Forces threatens massive civilian casualties and significant disruption to humanitarian assistance efforts."
It said the advance of Daglo's forces "has already caused large-scale displacement of civilians from Al-Jazira State... and the closure of markets in Wad Madani that many depend on."
Bombing in Nyala
In the western Darfur region, an army source told AFP that the air force struck military buildings, over which the RSF had announced its control in October, and the airport in Nyala, the state capital of South Darfur.
The source said "the RSF's Al-Zurq base, which is the main centre for supplies, was bombed."
FILE - People fleeing the violence in West Darfur, cross the border into Adre, Chad, August 4, 2023.
The "Emergency Lawyers" advocacy group said in a statement on Monday that the bombardment "hit populated neighborhoods at dawn today, and last Thursday the city witnessed bombing with explosive barrels that killed 10 civilians and left 37 injured."
The war between the army and the RSF has killed 12,190 people, according to conservative estimates by the Armed Conflict Locations and Events Data project.
It has displaced 5.4 million people inside the country, according to the UN, and sent over 1.3 million fleeing abroad.
Both sides in the conflict have been accused of indiscriminately bombing residential areas, using human shields, and robbing and harassing civilians.