JUBA: 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 said Tuesday.

Rights investigators from the UN mission in South Sudan (UNMISS) warned of “widespread human rights abuses” 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.

The military, the Sudan People's Liberation Army (SPLA), launched a major offensive against rebel forces in April, with fierce fighting in Unity state's northern Mayom district, once a key oil producing area.

“Survivors of these attacks reported that SPLA and allied militias from Mayom county carried out a campaign against the local population that killed civilians, looted and destroyed villages and displaced over 100,000 people," the UN statement read.

“Some of the most disturbing allegations compiled by UNMISS human rights officers focused on the abduction and sexual abuse of women and girls, some of whom were reportedly burnt alive in their dwellings.

“Civil war began in December 2013 when President Salva Kiir accused his former deputy Riek Machar of planning a coup, setting off a cycle of retaliatory killings that have split the poverty-stricken, landlocked country along ethnic lines.

The upsurge in fighting “has not only been marked by allegations of killing, rape, abduction, looting, arson and displacement, but by a new brutality and intensity,” the UN statement added.

“The scope and level of cruelty that has characterised the reports suggests a depth of antipathy that exceeds political differences.

“The UN children's agency said in a report earlier this month that warring forces have carried out horrific crimes against children, including castration, rape and tying them together before slitting their throats.

Two-thirds of the country's 12 million people need aid, according to the UN and one-sixth have fled their homes.