South Sudan says it is sending its army along the border with Sudan, following ethnic clashes that have killed more than 40 people.
The government has accused UN peacekeepers in the region of failing to protect civilians who live there.
The ethnic clashes are between the Ngok Dinka and the Misseriya Arab communities who cross from Sudan looking for pastures.
The two groups have long-running disputes that have displaced thousands of people over the years.
On Monday, nearly 30 people were killed in Leer county in the latest bout of fighting, which began in late February.