Thirteen United Nations workers in South Sudan kidnapped by rebels have been safely freed a week after their abduction, the UN said Monday.

Thirteen United Nations workers in South Sudan kidnapped by rebels have been safely freed a week after their abduction, the UN said Monday.

Around 100 rebel fighters, who have been battling the government for almost two years, seized 31 members of the UN peacekeeping mission in South Sudan (UNMISS) last week.

While 18 Bangladeshi peacekeepers were freed soon after they were held, the 13 remaining UN workers -- all South Sudanese nationals -- were released by the rebels on Sunday, UNMISS said Monday.

The UN had last week said only 12 were still being held. However, it said 13 were released on Sunday.

All were on a river barge carrying fuel for the UN mission. While the barge was also released, the UN said that rebels had stolen the 55,000 liters of fuel it was carrying, as well as communications equipment, an inflatable boat, and seven weapons.

UN chief in South Sudan Ellen Margrethe Loj said she was "relieved by the safe release of all UN personnel."

She had previously warned that the kidnap "may constitute a war crime."
The UN had last week said only 12 hostages were still being held. However, it said 13 were released on Sunday.

Some 12,500 peacekeepers are deployed in South Sudan, which has been wracked by conflict since December 2013.

Tens of thousands of people have been killed, and UN-backed experts have warned of the "concrete risk of famine" before the end of the year, if fighting continues and aid does not reach the hardest hit areas.

Both sides are accused of having perpetrated ethnic massacres, recruited and killed children and carried out widespread rape, torture and forced displacement of populations to "cleanse" areas of their opponents.