A ceasefire between South Sudan's government and rebels appeared to come into effect on Saturday following a deal to end a five-month war that has pushed the country to the brink of genocide and famine.

President Salva Kiir and rebel leader Riek Machar, a former vice president, met in the Ethiopian capital on Friday and agreed to order a halt to fighting within 24 hours.

Military officials from both sides told AFP news agency the frontlines appeared to be quiet on Saturday ahead of the deadline to implement the truce.

A previous ceasefire that had been agreed to in January quickly fell apart.

South Sudanese army spokesman Philip Aguer said on Saturday that the truce appeared to already be in place.

"As far as the information I have, there are not any skirmishes today," Aguer said.

"The rebels are under Riek Machar and it was Riek Machar who declared war against the government," he said, adding however that he feared "other forces not under the control of Riek Machar".

Under the deal, the rivals "agreed that a transition government offers the best chance to the people of South Sudan" with the promise of fresh elections for the world's youngest nation, said Seyoum Mesfin, head mediator with the East African regional bloc, the Intergovernmental Authority on Development (IGAD).

War crimes reports

Both sides also "agreed to open humanitarian corridors... and to cooperate with the UN" to ensure aid was delivered, Mesfin said.

The deal came as the United Nations food agency said there was only a "small window of opportunity" to avert famine in South Sudan.

The peace deal, which followed intense lobbying from world leaders, came amid new reports of war crimes committed by both sides and fears that a wave of ethnic killings could result in genocide.

The war has claimed thousands - and possibly tens of thousands - of lives, with more than 1.2 million people forced to flee their homes.

The conflict started as a personal rivalry between Kiir and Machar and has seen the army and communities divided along ethnic lines, pitting members of Kiir's Dinka tribe against Machar's Nuer.

The war broke out on December 15 with Kiir accusing Machar of attempting a coup. Machar then fled to launch a rebellion, insisting that the president had attempted to carry out a bloody purge of his rivals.

After Friday's signing ceremony in the city's presidential palace, Kiir said: "Now we have come to our senses...dialogue is the only answer to whatever problem we had. We will continue to move in the right direction."

PHOTO CAPTION

Map detailing the refugee, IDP situation in South Sudan.

Aljazeera