Tanzania, March 6 -- South Sudan's activist Peter Biar Ajak has been arrested and charged in the US for attempting to smuggle weapons worth $4 million to his country, potentially harming his profile as an activist seeking to tame graft.

The US Department of Justice said on Tuesday Mr Ajak, 40, and his compatriot Abraham Chol Keech, 44, were facing charges of conspiring to purchase and "illegally export millions of dollars' worth" of military-grade weapons to South Sudan.

They wanted to export the arms under a false contract, the charges said.

Those weapons included automatic rifles, grenade launchers, Stinger missile systems, hand grenades, sniper rifles, ammunition, and other export-controlled items from the United States to South Sud...