South Sudan clashes
Men carrying boxes walk past United Nations Mission in Sudan (UNAMIS) personnel who are guarding people displaced by recent fighting, in Jabel, on the outskirts of capital JubaReuters

The UN has given its approval for doubling the number of peacekeepers in landlocked South Sudan as violent clashes in the last few days are said to have killed "thousands" of people.

The Security Council has authorised the deployment following a request from UN Secretary General Ban Ki-moon and raised the number of troops to 12,500 from 7,000. This is in addition to the expansion of the police force from 900 to 1,323.

The additional troops are to be drawn from Liberia, Abyei, Democratic Republic of Congo and Ivory Coast.

South Sudan, the world's youngest nation, has been witnessing bloody violence over the last few days as rival armed groups launch relentless attacks on each other.

When asked what would be the estimated death toll, UN humanitarian co-ordinator Toby Lanzer in the county, told reporters: "Absolutely no doubt in my mind that we're into the thousands."

UN officials have also found two new mass graves in the capital Juba, apart from the previously discovered one in the oil-rich town of Bentiu. The authorities, however, revised the body count in Bentiu to 34 against the earlier 75.

Earlier reports said the conflict is gradually turning into an ethnic war between the two main tribal groups Dinka and Nuer.

In a Christmas message to the country, President Salva Kiir, who hails from the Dinka tribe, said: "There are now people who are targeting others because of their tribal affiliation. It will only lead to one thing and that is to turn this new nation into chaos."

Government troops were blamed for gunning down dozens of Nuer tribes in Juba neighbourhoods. However, senior army officials have denied targeting people based on ethnicity.

"There is a palpable fear among civilians of both Dinka and Nuer backgrounds that they will be killed on the basis of their ethnicity," said the UN High Commissioner for Human Rights Navi Pillay.