By Tom Odula and Jason Straziuso

NAIROBI // South Sudan’s government on Friday agreed to end hostilities, regional leaders said at the end of a crisis summit, raising hopes for a potential breakthrough in efforts to cease violence that has displaced more than 120,000 people in the world’s newest country.

East African leaders meeting in Kenya under a bloc called IGAD said in a statement on Friday that they “welcomed the commitment by (South Sudan’s government) to an immediate cessation of hostilities.”

But the former vice president, Riek Machar, the political rival of the South Sudanese president, Salva Kiir, who is accused of orchestrating a failed coup that the government says sparked unrest across the oil-producing country, was not represented at the summit in the Kenyan capital of Nairobi.

The leaders’ joint statement said Mr Machar is urged to “make similar commitments” to end hostilities.

Mr Machar, the alleged leader of renegade forces now in control of some parts of South Sudan, remains a fugitive wanted by the military. At least 10 of his political allies were detained for their roles in the alleged coup plot.

On Friday, the South Sudanese government released two of the detained, according to the presidential spokesman, Ateny Wek Ateny. However, the government will keep three of the group in custody over corruption allegations.

Mr Machar denies there was a coup attempt, and some officials with the ruling party insist violence broke out when presidential guards from Mr Kiir’s majority Dinka tribe tried to disarm guards from the Nuer ethnic group of Machar, leading to wider military clashes along ethnic lines.

Mr Machar, an influential politician who appears to command the loyalty of Nuer army officers, has criticised Mr Kiir as a dictator and says he will contest the 2015 presidential election. Mr Kiir had fired Mr Machar as his deputy in July following a power struggle within the ruling party.

In a speech at the Nairobi summit, the Kenyan president, Uhuru Kenyatta, had noted that there is “a very small window of opportunity to secure peace” in South Sudan, where fighting since December 15 has raised fears of full-blown civil war.

The number of internally displaced people continues to rise, with many seeking shelter at UN compounds across the country. There are sporadic military clashes in the oil-rich states of Unity and Upper Nile, potentially endangering the oil revenues that South Sudan depends on to keep the government running.

The UN said aid agencies need at least $166 million (Dh610 million) to save lives.

The top UN humanitarian official in South Sudan, Toby Lanzer, said earlier this week that he believes the death toll has surpassed 1,000. The UN also is investigating alleged mass killings in the latest violence.

“We have heard reports of extra-judicial killings, arbitrary detentions of civilians, ill-treatment, abuse and also mass graves,” said Hilde Johnson, head of the UN mission in South Sudan. “Our human rights officers have been working around the clock, throughout this crisis, and they are investigating these reports and allegations.”

* Associated Press with additional reporting by Reuters