At least 140 people have been killed in ethnic¹ clashes in Southern Sudan, officials say, as aid agencies warn that the country faces a return to war.

苏丹南部地区发生种族冲突，至少140人丧生。援助机构发出警告，苏丹面临内战危险。

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Nuer and Dinka people have a long history of rivalry

Deputy governor of Warrap state Sabino Makana said members of the Nuer努尔人 group attacked Dinka丁卡人 cattle herders牧人，监狱看守 and seized thousands of animals.

Most of the violence happened over the weekend in very remote areas, he said.

The UN says more than 2,000 people have been killed in ethnic violence in the south since January 2009.

More people died in Southern Sudan than in Darfur达尔富尔 last year.

'Lethal³ cocktail⁴'

The BBC's Peter Martell in the southern capital Juba says the Nuer and Dinka people have a long history of both rivalry and co-operation.

He says the latest clashes came to light曝光，泄露 only after a UN security team flew over the area around the city of Tonj two days ago.

Senior UN official Lise Grande said it was a "matter of deep concern".

"Local sources on the ground said that at least 140 people had been killed, 90 wounded and 30,000 head of cattle had been stolen," she said.

The Warrap state deputy governor told Reuters路透社 news agency that the Nuer attackers killed 139 Dinka herders and wounded dozens more on Saturday.

He said many of the Nuers also died, but he did not have reliable可靠的 figures.

The north and south fought a 22-year civil war that left some 1.5 million people dead.

A 2005 peace deal ended the conflict and created a power-sharing government.

But 10 international aid agencies warned on Thursday that a "lethal cocktail" of rising violence, chronic⁵长期的，慢性的 poverty and political tensions was pushing the accord一致，协议 towards collapse⁶.

Southern politicians accuse President Omar al-Bashir's allies of arming rival groups in the south to stoke up添燃料 trouble.

They say Mr Bashir wants to destabilise the region to sabotage⁷妨害 a national election planned for April, and a referendum公民投票，全民公决 on southern independence the following year.

Southern Sudan remains⁸ one of the poorest areas of the world and clashes over resources are common.