Evidence is emerging of mass ethnic killings amid the deepening conflict in South Sudan.

The United Nations says a grave containing 75 bodies has been found and other eyewitness accounts speak of hundreds being shot by security forces.

For the first time since World War II, Japan has provided ammunition to another country, supplying South Korean peacekeepers in South Sudan.

The UN Secretary-General Ban Ki-moon wants almost to double the size of its 7,000-strong peacekeeping force in the African country.

Samantha Power, US Ambassador to the United Nations, said: “To immediately address the dire situation, the Secretary General has requested the security Council to authorise an additional 5,000 peacekeepers for UNMISS (United Nations Mission in South Sudan) and the United States is one of many council members, in fact all council members, that fully supports this proposal – to ensure that the mission has the assets and resources that it needs to fulfil its mandate.”

The ambassador added that as long as South Sudan’s president and rebel leader remained at loggerheads, innocent people were being killed on nothing other than ethnic grounds.

President Salva Kiir, a Dinka, and his Nuer former deputy Riek Machar have both indicated they are ready to talk.

A government official, however, said South Sudan would not meet Machar’s demand that detained opposition leaders be released.

Meanwhile on the ground, the conflict between Dinka and Nuer groups has intensified.

At Bor in Jonglei state, thousands are seeking protection at a UN compound and in churches.

In the country overall it is thought the number killed may vastly exceed the official figure of 500.

According to the UN’s humanitarian coordinator, there are probably more than 100,000 internal refugees.

After decades of conflict in the region, South Sudan gained independence in 2011, and remains today the world’s newest country.