South Sudan’s president has reached a ceasefire agreement with a rebel leader, a US official has said, after a vicious cycle of revenge killings drew international alarm.

South Sudan’s president has agreed to meet his rival as soon as next week to jump-start peace talks that have been stalled for months, US secretary of state John Kerry said.

Two warring factions from South Sudan are holding more advanced peace talks for the first time since conflict began in the country on December 15.

An African official who is working to organise peace talks between warring parties in South Sudan said that direct talks between the sides have been delayed.

Rebel forces in South Sudan must accept that “taking power by force cannot work”, the country’s foreign minister said as the two sides in a bloody conflict prepared for peace talks.

Rebels in South Sudan took control of nearly all of a strategic city, even as the government and fighters agreed to hold talks for the first time.

Fresh fighting has erupted in Bor, the contested capital of South Sudan’s Jonglei state, as rebels move to retake control from government troops.

Twenty-five thousand young men who make up a tribal militia known as the “White Army” are marching towards a contested state capital in South Sudan, an official has said, reducing hopes for a ceasefire.

South Sudan’s government has agreed at a meeting of East African leaders to end hostilities against rebels accused of trying to overthrow the young country’s regime, but the ceasefire was quickly thrown into doubt because the head of the rebellion was not invited.

Sporadic gunfire rang out in the South Sudanese capital, Juba, overnight as the military “cleared out remnants” of a faction of soldiers accused of mounting a coup attempt, the country’s foreign minister said today amid an ongoing hunt for the former deputy president who is accused of leading the failed plot.

The chief mediator of talks aimed at ending northern Uganda’s civil war has called both sides back to talks next week, but acknowledges the rebels might not come.

Ugandan rebel leader Joseph Kony has told journalists that he is committed to negotiating peace after 19 years of war, and denied he has committed war crimes.