South Sudan army use force at UN base: Spokesman

South Sudan government troops tried to force their way into a United Nations compound sheltering thousands of civilians after taking a key town from opposition rebels, a UN spokesman said.

Senior government figures and troops threatened UN staff when they tried to enter the compound at Bor, Martin Nesirky said in a statement condemning the tactics.

Secretary General Ban Ki-moon "is alarmed at the attempt today by senior members of the government of South Sudan and South Sudan army to force entry into the protection of civilians site," Nesirky said.

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 Saturday.

The UN Mission in South Sudan (UNMISS) says it faces growing threats from both sides as they shelter tens of thousands of civilians in compounds across the country.

Aid groups say up to 10,000 people have been killed in the conflict, which erupted on December 15.

Highlighting the "devastating" impact of the hostilities on the world's newest nation, 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 UNMISS protection site today."

"The secretary general condemns the threats made against UN personnel and demands that all parties to the conflict respect the sanctity of UNMISS protection sites," said Nesirky.

He added that it was "just one of a growing number of violations" of the UN accord with the South Sudan government "making it increasingly difficult for UNMISS to implement its mandate and dangerous for United Nations staff working in South Sudan.