No fewer than 16 people were killed in the South Sudanese town of Wau on Monday, said the United Nations, as witnesses said ethnic militiamen went house to house searching for people from other groups.

Streets were deserted as families hid inside, residents told Reuters by phone. Some reported seeing killings.

Witnesses said the militia members were aligned with the government in the country’s ethnically charged civil war. They accused army soldiers of blocking the main road to a civilian encampment protected by U.N. peacekeepers.

U.N. spokesman Stephane Dujarric said two U.N. peacekeeping patrols had been sent to the area on Monday and more were expected to patrol on Tuesday. The U.N. peacekeeping mission is known as UNMISS.

“They saw 16 bodies of civilians in a hospital and at least 10 others were injured,” Dujarric told reporters in New York.

“Eighty-four people have arrived at the UNMISS protection of civilians site in Wau, while at least 3,000 people have reportedly moved to a site run by the Catholic church in town and those are mostly women and children,” he said.

South Sudan‘s deputy army spokesperson, Colonel Santo Domic Chol, said fighting had first broken out during a mutiny by soldiers at the town’s prison. He was awaiting more information, he said.

The fighting followed an ambush that killed a brigadier general and a colonel in Wau state over the weekend, a rebel spokesman based outside the country said.

“This morning the government forces were retaliating against innocent Fertit people,” he said, referring to a local ethnic group.

The International Committee of the Red Cross said it is flying a surgical team to Wau.

“The ICRC has received multiple requests to assist medical staff in Wau with patients wounded in the violence,” a spokesman said.

A staff member at Wau Teaching Hospital said all the bodies it had received appeared to be civilian and all had gunshot wounds.

Five residents, all of whom asked not to be named, described members of the president’s Dinka ethnic group searching for members of the local Luo and Fertit groups. The head of the military is also Dinka.

“We are still inside hiding,” said one man by telephone, speaking from a Wau neighbourhood called Nazareth. “I have seen four dead bodies of my neighbours.”

“Armed militias are moving from house to house,” one resident said. “It is an ethnic crackdown.” Another said he had fled an attack that had killed many people, including his cousin.

South Sudan descended into civil war in 2013 after President Salva Kiir, a Dinka, fired his deputy, Riek Machar, a Nuer. Fighting since then has often split the oil-producing country along ethnic lines and created a patchwork of armed factions.

The country is awash with weapons after decades of conflict with neighbouring Sudan and local feuds over land.