A US district court has charged a prominent South Sudanese activist, Peter Biar Ajak, with conspiring to purchase and illegally export weapons worth millions of dollars.
He was charged alongside his compatriot Abraham Chol Keech.
They are accused of colluding to buy weapons such as automatic rifles, grenade launchers, Stinger missile systems, hand grenades and other export-controlled items from the US to South Sudan.
They have not commented on the allegations.
The sale of weapons to South Sudan is prohibited by two US laws.
South Sudan has also been subject to an arms embargo by the UN Security Council that was initially imposed in 2018 and has been renewed several times since then.
The court said that as part of the illegal scheme to smuggle the weapons, the accused agreed to a $4m (£3.5m) contract worth of weapons and related items.
They also requested a “fake contract” in the same amount for consulting services and items such as communications equipment for use in refugee camps, a statement by the US Justice Department said.
Mr Ajak, a Harvard fellow and a vocal critic of President Salva Kiir’s government, was arrested in 2018 and sentenced to two years in prison.
He was pardoned by the president in January 2020.
South Sudan’s foreign affairs ministry has not yet commented on the arrest of the two.