The United Nations said on Thursday that a dozen contractors seized by South Sudan rebels on Monday have not yet been released.

Around 100 rebels in South Sudan on Monday detained the crew of a barge on the Nile River carrying fuel for a United Nations mission. The rebels were heavily armed with two tanks and also seized weaponry and equipment.

The barge crew was made up of 18 Bangladeshi peacekeepers and 12 Sudanese contractors. The group was captured north of Malakal in the upper Nile state and later taken to the town of Kaka.

The 18 peacekeepers were freed on Thursday after being held for three days in captivity.

The UN first reported that 20 peacekeepers were originally involved in the incident, but later corrected the number to 18. The UN demanded the release of the crew of 12 still in captivity.

UN spokesman Stephane Dujarric demanded that the crew be “released immediately, unharmed and unhurt” and called on rebel leader Riek Machar to “take his responsibilities” and “uphold his commitment to the United Nations that all be returned safely.”

The spokesman warned further that attacks against the peacekeepers could be punishable as war crimes.

UN peacekeeping chief Herve Ladsous also called Machar by phone and personally appealed for the release of those still captured.

The Sudan Tribune reported that the barge had already been released on the demands of rebel leader Riek Machar.

South Sudan has seen tens of thousands of people killed in a power struggle between President Salva Kiir (R) and his former deputy Riek Machar (L)

Around 12,500 peacekeepers have been sheltering around 100,000 South Sudanese nationals at camps since December 2013. Peacekeepers have been deployed in the country since it declared independence from Sudan in 2011 in an attempt to aid the poverty-stricken country.

The country has seen tens of thousands of people killed and 2 million people displaced since a power struggle began between South Sudan President Salva Kiir and his former deputy Riek Machar.

A peace deal was signed by Kiir and Machar in August, but tensions remain as both sides have accused each other of attacks.

smm/bw (AFP, dpa, Reuters)