One resident, who requested anonymity for their safety, told AFP that Mohamed Hamdan Dagalo's Rapid Support Forces, RSF, shot at dozens of people in the village of Baranko last week.
The testimony adds to a litany of abuses during more than 10 months of war between Dagalo's forces and Sudan's army led by Abdel Fattah al-Burhan.
On Friday, the United Nations human rights chief said Sudanese civilians are living in "sheer terror" and both sides had consistently acted with impunity for multiple rights violations.
"On February 22, the militia fired on dozens of residents who were protesting against the arrest of several young people guarding the houses," said a resident of Baranko, about halfway between state capital Wad Madani and Khartoum to the north.
Multiple local sources reported 18 wounded in the shooting, a few of whom managed to reach a hospital in Shendi, 250 kilometers to the north, by taking side roads.
Breaking the communications siege via a rare satellite phone call, the anonymous resident told AFP that young men have been taking turns guarding houses at night.
It is a modest attempt to protect the homes from pillage, a signature RSF tactic.
The paramilitary force is the descendant of the Janjaweed militia, which began a scorched earth campaign in Sudan's western Darfur area more than two decades ago under strongman Omar al-Bashir.
FILE - Supporters and members of the Sudanese armed popular resistance, which backs the army, raise weapons on a pick up truck during a meeting with the city's governor in Gedaref, Sudan, on Jan.16, 2024 amid the ongoing conflict in Sudan between the army and paramilitaries.
Washington has accused both sides of war crimes, and said the RSF also carried out ethnic cleansing and crimes against humanity.
Al-Jazira, in central Sudan, had become a refuge for those fleeing the fighting in and around the capital Khartoum.
But in December, the RSF swept into the former breadbasket and proceeded to kill and plunder, witnesses told AFP at the time.
The war has killed thousands, uprooted eight million people and led the country to the edge of famine, aid agencies have warned.
According to UN figures, nearly half a million people had sought refuge in Al-Jazira, including in Wad Madani, but the fighting eventually caught up with them there too, sending thousands fleeing again.