The U.S. State Department has ordered nonemergency government personnel to leave South Sudan’s capital as tension escalates because of fighting in the north.

The travel advisory level for South Sudan remains at Level 4, which means Americans should not travel to the African country.

As fears grow of a renewed full-blown civil war, the United States on Sunday ordered all its non-emergency staff to leave the country.

On Friday, a South Sudanese general and dozens of soldiers were killed when a U.N. helicopter trying to evacuate them from Nasir came under attack, the government said.

Hassan Sheikh Mohamud holds talks over phone with South Sudanese President Salva Kiir as well as Vice President Riek Machar, Kiir's rival

Tensions are running dangerously high after an opposition-linked militia overran an army base loyal to President Salva Kiir in South Sudan's Upper Nile state. Regional leaders should urgently press Kiir and Vice President Riek Machar,

A crew member was killed and two others were injured when a United Nations helicopter on an evacuation mission in a remote part of South Sudan was attacked.

The aircraft came under fire as it tried to rescue wounded soldiers, the United Nations said. The attack came amid fears that a critical power-sharing deal was at risk of collapse, risking all-out civil war.

The United States has ordered its non-emergency government personnel in South Sudan to leave the country because of security concerns, the State Department said on Sunday. "Armed conflict is ongoing and includes fighting between various political and ethnic groups.

South Sudan's political landscape is tense as forces loyal to President Kiir arrest key allies of Vice President Machar, including the Peacebuilding Minister. This moves jeopardize the peace deal between the factions.

President William Ruto has urged South Sudan President Salva Kiir and the first Vice President Riek Machar to engage in dialogue in a bid to foster peace.