SOUTH Sudan's army raped, then torched girls alive inside their homes during a recent campaign notable for its "new brutality and intensity", a UN rights report says.

RIGHTS investigators from the UN mission in South Sudan (UNMISS) warned of "widespread human rights abuses" including gang-rape and torture in a report based on 115 victims and eyewitnesses from the northern battleground state of Unity, scene of some of the heaviest recent fighting in the 18-month-long civil war.