Two gunmen have attacked an office of the UN refugee agency in southern Sudan, killing a local guard and wounding two workers, the agency says.
The UNHCR said it was still seeking more details about the attack in the southern town of Yei.
Following the attack, the planned return of refugees in Democratic Republic of Congo has been suspended.
The UNHCR says there are still 350,000 Sudanese refugees in neighbouring countries follwing a 21-year war.
More than 13,000 refugees are in DR Congo.
The two wounded UNHCR employees are being treated in hospital in the southern capital, Juba, before being airlifted in Nairobi, Kenya.
UN High Commissioner for Refugees Antonio Guterres said the attack was a "shocking" event.