DHAKA: Thousands of people must have been killed in the past week of violence in South Sudan, the top UN humanitarian co-ordinator there has told the BBC.
Toby Lanzer, who is in Bentiu in northern Unity state, said it had been "a devastating week for South Sudan".
The UN Security Council on Tuesday voted unanimously to almost double the number of peacekeepers to 12,500, reports BBC.
Earlier President Salva Kiir said his forces had recaptured the key town of Bor days after it was seized by rebels.
The rebels are led by Riek Machar, of the ethnic Nuer, who has been battling President Kiir, of the Dinka.
The UN also said on Tuesday that it had reports of at least three mass graves.
One was in Bentiu in the north, and two in the capital, Juba.
In a Christmas message, Kiir said "innocent people have been wantonly killed", adding: "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."
`Palpable fear`
Lanzer told the BBC`s Newshour programme: "I think it`s undeniable at this stage that there must have been thousands of people who have lost their lives.
"When I`ve looked at the hospitals in key towns and I`ve looked at the hospitals in the capital itself, the range of injuries, this is no longer a situation where we can merely say it`s hundreds of people who`ve lost their lives."
Lanzer also said that the number of people seeking shelter from the fighting was "tens of thousands if not hundreds of thousands".
He said that the tensions between different communities in South Sudan was even evident within a UN base he had just visited where some 7,500 people are seeking protection.
The UN High Commissioner for Human Rights, Navi Pillay, said: "There is a palpable fear among civilians of both Dinka and Nuer backgrounds that they will be killed on the basis of their ethnicity."
The UN says at least 80,000 people have been displaced by the South Sudan crisis - about half of them seeking shelter with the UN.
Late on Tuesday the UN Security Council voted to increase its peacekeepers from 7,000 to 12,500, and its international police force from 900 to 1,323.
The BBC`s James Copnall explains the fighting gripping the world`s newest state, South Sudan - in 60 seconds
It authorised temporary transfers from missions in DR Congo, Darfur, Abyei, Ivory Coast and Liberia.
The council called for "an immediate cessation of hostilities and the immediate opening of a dialogue".
BDST: 0828 HRS, DEC 25, 2013
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