Locals pretending to be peaceful protesters delivering a petition forced their way into the camp on Thursday and opened fire before being beaten back by UN security personnel (UNMISS).
"The army has come in now. They have been ordered to protect UNMISS so there will be no attack from anybody," Ateny Wek Ateny, President Salva Kiir's spokesman said. Thousands of people have been killed and more than one million displaced since fighting erupted in South Sudan in the middle of December, triggered by a power struggle between Kiir and former vice-president Riek Machar.
The conflict in Africa's newest state took on a tribal dimension as Kiir's Dinka fought Machar's Nuer for control of strategic towns before a ceasefire was signed on January 23.
Sporadic clashes between both sides after the ceasefire deal erupted into full-blown combat this week, when the rebels seized control of Bentiu, the capital of oil-producing Unity state.
The conflict has disrupted oil production, which provides most government revenue.