South Sudan government troops tried to force their way into a United Nations compound where thousands of civilians were sheltering from violence in the country, the UN said.

Senior government figures and troops threatened staff when they tried to enter the UN compound in Bor, said Martin Nesirky, the spokesman for UN secretary-general Ban Ki Moon.

Bor has been repeatedly lost and retaken by government forces in the worsening conflict between President Salva Kiir and his former vice-president Riek Machar.

The government said it retook Bor again on Saturday and reportedly tried to enter the camp the next day.

The UN Mission in South Sudan (Unmiss) says it faces growing threats from both sides as they shelter nearly 70,000 civilians in compounds across the country.

Highlighting the "devastating" impact of the hostilities, Mr Ban said he was "particularly disturbed that United Nations staff were threatened by South Sudan military when they refused to allow armed soldiers to accompany civilians to visit the protection site today.

"The secretary-general demands that all parties to the conflict respect the sanctity of protection sites," said Mr Nesirky.

He added it was "just one of a growing number of violations" of the UN accord, "making it increasingly difficult for Unmiss to implement its mandate and dangerous for UN staff working in the country."

The UN said thousands of civilians had been "killed, brutally abused and left homeless in just over a month of conflict."