A pair of grim reports detailed the worsening crisis unfolding in South Sudan, with the United Nations stating that crimes against humanity had likely occurred and a rights group releasing evidence of dozens of mass graves, child rape and grotesque mutilation of civilians.

Amnesty International published a report containing scores of testimonies of "war crimes" in the world's youngest nation.

Meanwhile, the U.N. said its peacekeeping body in the country had found “reasonable grounds to believe that crimes against humanity have been committed during the conflict by both government and opposition forces.”

The international body warned of "countless" gross violations of human rights.

Amnesty’s study documented evidence to back up the claim. Through its report the organization catalogued human rights abuses by government troops loyal to President Salva Kiir, an ethnic Dinka, and rebels loyal to former Vice President Riek Machar, an ethnic Nuer.

The country has been dogged by unrest, with widespread violence breaking out in mid-December. Since then, at least 10,000 people have been killed and an estimated 1 million displaced.

"The ethnic dimensions of the conflict are deepening as fighters engage in reprisal attacks, continuously escalating the cycle of violence," Amnesty said.