JUBA (AFP) ― South Sudan’s government said Saturday that fighting in the country’s five-month civil war appeared to have stopped as a cease-fire with rebels came into effect following a peace deal.

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

The agreement came after massive international pressure on both sides to stop a conflict marked by widespread human rights abuses, a major humanitarian crisis and fears the world’s youngest nation was on the brink of a genocide and Africa’s worst famine since the 1980s.

“The situation is calm. We have not received any attacks since this morning,” South Sudan’s defense minister, Kuol Manyang, said late Saturday.

Several independent aid agencies also confirmed that major frontlines around key towns were quiet throughout the day. Kiir and Machar had agreed to a cease-fire in January, but that deal quickly fell apart.

The United Nations food agency meanwhile warned there was only a “small window of opportunity” to avert famine, and appealed for relief agencies ― who have been subjected to armed attacks and looting ― to be allowed unfettered access.

In their deal, Kiir and Machar agreed to form a transitional government and hold fresh elections, and “open humanitarian corridors ... and to cooperate with the U.N.” to ensure aid is delivered.

The peace deal, which followed intense lobbying from world leaders and Washington slapping sanctions on senior military commanders, 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.

U.S. Secretary of State John Kerry, who was in South Sudan earlier this month to push for peace, said the agreement “could mark a breakthrough.”

“The hard journey on a long road begins now and the work must continue,” Kerry said in a statement, urging “both leaders to take immediate action now to ensure that this agreement is implemented in full and that armed groups on both sides adhere to its terms.”

European Union foreign affairs head Catherine Ashton warned that “humanitarian calamity beckons” and that “the rapid implementation of this agreement is the only way large numbers of South Sudanese can be spared from violence and famine.”

U.N. Secretary-General Ban Ki-moon, who also visited the country last week, appealed to Kiir and Machar to “immediately translate these commitments into action on the ground.”

Oxfam, one of a handful of aid agencies working in the worst-affected areas of the country, said the deal was a “timely breakthrough” but warned that South Sudan still needed a “mammoth aid effort.”

“Civilians caught up in this bloody conflict need to have full confidence that they can return to their homes without fear of violence,” said Cecilia Millan, Oxfam’s local head.

“They need to get back to their fields to plant their crops as soon as possible or they will lose the chance of feeding their families.”

The World Food Program said “a hunger catastrophe can still be avoided, but humanitarian agencies must be allowed to reach tens of thousands of people in need before it’s too late”.

U.N. rights chief Navi Pillay, a former head of the U.N. genocide court for Rwanda, said she recognised “many of the precursors of genocide” listed in a U.N. report on atrocities that was released during the week.

These included broadcasts urging rape and “attacks on civilians in hospitals, churches and mosques, even attacks on people sheltering in U.N. compounds -- all on the basis of the victims‘ ethnicity.”

Testimonies in a report this week by Amnesty International describe civilians, including children, executed by the side of the road “like sheep” and other victims “grotesquely mutilated” with their lips sliced off.

The conflict, which started as a personal rivalry between Kiir and Machar, has seen the army and communities divide 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 the bush to launch a rebellion, insisting that the president had attempted to carry out a bloody purge of his rivals.

Observers believe implementing the truce will be tough for both sides.

“Of course this is a very difficult issue. Some of the field commanders tend to be behaving in their own way without any instructions from above. So we can still expect some rocky roads ahead,” said Simon Monoja Lubang, a lecturer at the University of Juba.