South Sudanese rebels have accused the government of violating their latest ceasefire deal, just hours after both sides pledged to end almost a year of fighting.

Taban Deng Gai, negotiator for the ethnic Nuer rebels loyal to former vice president Riek Machar, said on Saturday government troops had "advanced from Bentiu and Pariang and attacked our positions at Tor and Hofra in Unity state".

Unity is South Sudan's oil hub and saw fighting last month. Neither the government of President Salva Kiir, an ethnic Dinka, nor the eight-nation regional bloc IGAD, were available for comment.

Seyoum Mesfin, chief mediator in the conflict, had announced earlier in the day, after two days of talks in the Ethiopian capital Addis Ababa, that both sides had agreed to cease hostilities unconditionally and bring the war to an end.

"The parties commit to an unconditional, complete and immediate end to all hostilities, and to bring the war to an end," said Seyoum, adding that they had also pledged to stop recruiting and mobilising civilians.

Sanctions threat

The former Ethiopian foreign minister told reporters that IGAD had granted the two sides 15 days to conduct further consultations, and said it had agreed to punish any party that violated the agreement with asset freezes and travel bans, among other measures.

He said IGAD would also stop the supply of arms and ammunition to any side that carried on fighting.

"The IGAD region shall, without further reference to the warring parties, take the necessary measures to directly intervene in South Sudan to protect life and restore peace and stability," he said.

Machar welcomed the deal, saying: "We do not want any soldier or any civilian to die again after this progress in Addis Ababa."

Kiir, for his part, ordered troops from the national army to stay in their barracks in compliance with the agreement.

"Should they be attacked from any direction, they should only fight in self-defence," Kiir said.

The European Union and the United States have already imposed sanctions on both sides for frequent breaches of a first peace agreement signed in January, and threatened more.

The internal conflict in South Sudan, which declared independence from Sudan in 2011, has killed more than 10,000 people, driven 1 million from their homes and raised the spectre of famine.

Source: Agencies