South Sudanese government troops are staging "door-to-door" raids in a town seized from opposition forces, the United Nations said Wednesday as more people took refuge in UN compounds.
The United Nations and aid groups have raised concerns over events in the Upper Nile state capital of Malakal since President Salva Kiir's forces seized it Monday from troops of former vice president Riek Machar in heavy fighting.
The UN mission "has received reports of the Sudan People's Liberation Army (SPLA) conducting house-to-house searches in Malakal," said Vanina Maestracci, a UN spokeswoman.
"The mission is investigating reports about the alleged extrajudicial killing of a pastor as well as killings of other civilians in the Malakal area in recent days."
The conflict in South Sudan has taken on an increasingly ethnic edge since it erupted on December 15. Kiir is an ethnic Dinka, while his rival is from the Nuer group.
Aid groups say up to 10,000 people have been killed in the conflict and UN officials say "mass atrocities" have been committed by both sides.
Around 72,000 people are now sheltering in eight UN compounds across South Sudan that have had to expand their protection zones to take thousands of extra people, according to the world body.
It said there are now more than 22,000 people at its Malakal base and more than 10,000 people in Bor, the Jonglei state capital retaken by government forces from Machar this week.
UN leader Ban Ki-moon has already protested over threats made to UN forces in an incident when a South Sudan minister tried to enter the Bor compound on Sunday.
More incidents have been reported, according to Maestracci.
UN Mission in South Sudan staff "continue to be threatened and harassed as they conduct their mandated duties," the spokeswoman said.