Rebels in South Sudan have seized UN river barges they suspect were transporting weapons for government troops, and are holding 16 peacekeepers.
The barges were taken along the White Nile in a disputed area in the volatile state of Upper Nile.
A spokesman for rebel leader Riek Machar said the barges were seized but did not specify how many.
Two government soldiers, three officers of the national security agency, and six barge technicians were also detained, according to Nyagwal Ajak Dengkak, a spokesman for another rebel commander who controls the area.
He added in a statement that rebel forces are taking “tough action against our enemies captured including UN soldiers currently disarmed and jailed for the world to know the truth of conspiracy between” the South Sudanese military and the UN mission.
The UN troops in detention will be treated “like criminals”, Mr Dengkak said.
The barges were seized at Kaka, a settlement on the rebel-controlled west bank of the river. The east side, where the UN mission has bases, is held by government troops.
UN spokeswoman Ariane Quentier said the mission is dealing with the situation.
Tens of thousands of people have died in South Sudan’s civil war and more than two million are displaced, according to the United Nations.
President Salva Kiir and rebel leader Mr Machar signed a peace deal in August but fighting has continued.
African Union investigators said in a report released on Tuesday that they discovered atrocities by both sides in the conflict, including testimony of forced cannibalism and the discovery of mass graves.