Barrel bombs believed to contain a highly flammable liquid have been used in airstrikes in South Sudan as escalating violence pushes the world's newest country to the brink of another civil war, the UN has said.

The top U.N. official in South Sudan is warning that the country is teetering on the edge of renewed civil war.

South Sudan’s embattled vice president said the deployment of Ugandan troops in his country violates a United Nations arms embargo and risks collapsing a peace accord, as the UN warned the oil-producing nation is on the brink of civil war.