Frequent clashes have taken place in Abyei region between rival factions of the Dinka ethnic group because of a dispute over the location of an administrative boundary where significant tax revenue is collected from cross-border trade.
Abyei is an oil-rich area that is jointly administered by South Sudan and Sudan, which have both staked claims to it. The region's information minister, Bulis Koch, said: "In the attacks that took place on February 2 and 3, several markets were set on fire, property looted and altogether 19 civilians got killed and 18 others were wounded."
A further 18 people were killed in separate attacks on Sunday, he said. Among those killed were three children and a local staff member working for Medecins Sans Frontieres (MSF). The clashes also displaced hundreds of people, who sought refuge in the compound of the United Nations Interim Security Force for Abyei (UNISFA) peacekeeping force.
Koch said young men from neighboring Warrap state and from a militia linked to rebel and spiritual leader Gai Machiek had taken part in the violence.
Warrap State's information minister Willima Wol, MSF South Sudan and UNISFA did not immediately respond to requests for comment.
In late January at least 54 people including women, children and two U.N. peacekeepers were killed in attacks in the same area.
More than 2,000 people were now sheltering at UNISFA's compound due to the fighting in January and this past weekend, Koch said.