Humanitarian agencies have warned that two weeks of fighting in the oil-rich region of Abyei on the border between Sudan and South Sudan have led to widespread displacement and hindered efforts to distribute aid.
Both countries jointly administer Abyei and claim ownership of the region.
The clashes have been linked to conflict between rival factions of the Dinka ethnic group – called the Ngok and the Twic.
Close to 100 people including UN peacekeepers have been killed.
Britain, the US and Norway – known as the Troika – have called on the South Sudanese government to hold accountable those behind the attacks.
Save the Children also says there have been incidents of looting of health and nutrition supplies at one of its health facilities.
The UN says more than 2,200 people, most of them women and children, are sheltering at one of its compounds in Rumajak, about 7km (4 miles) north of Abyei town. The humanitarian body also says it is beefing up land and air patrols to deter further violence.
