South Sudanese government officials and representatives of rebel groups agreed to face-to-face talks on a monitored ceasefire, with artillery fire in Juba's government district underlining the risk of all-out civil war.
The warring parties assured mediators they will strive to reach a political solution to the conflict that began in mid-December, Ethiopian envoy Seyoum Mesfin told reporters in Addis Ababa on Saturday.
There have been continued clashes between President Salva Kiir's SPLA government forces and rebels loyal to former vice president Riek Machar centred around the strategically located town of Bor. As delegates smiled in a luxury hotel in Ethiopia, heavy explosions from artillery fire were heard in a Juba district where most ministries, the presidential palace and the parliament are located.
It was not clear who was involved in the fighting, that ended a period of relative calm in the capital.
Conflict broke out on December 15 after Kiir accused his former deputy of trying to stage a coup. The violence spread swiftly, pitting members of Kiir's ethnic Dinka community against Machar's Nuer group.
The United Nations has estimated that "thousands" of people have died and about 200,000 have been displaced. Western and regional powers, many of which supported the negotiations that led to South Sudan's independence from Sudan in 2011, are pressing for a peace deal, fearing the new fighting could slide into civil war and destabilise East Africa.
Machar and his allies are demanding the release of all 11 politicians that Kiir's government has detained and for those individuals to be given freedom of movement, said Taban Deng Gai, head of the rebels' negotiating team.
The politicians are "languishing in jail not for any crimes they've committed, but for the reason of voicing their political opinion," Gai said.
Ugandan military forces also should withdraw from the country as part of a ceasefire, he said. Uganda said it sent troops into neighbouring South Sudan to protect its citizens. Rebels claim the Ugandan forces are supporting Kiir's troops.
Those detained in the wake of the alleged coup attempt include Pagan Amum, the former secretary general of the ruling Sudan People's Liberation Movement.
The government should release the detainees so they can join talks to end the political crisis, Donald Booth, the US envoy to Sudan and South Sudan, said.
Alexander Rondos, the EU envoy, said the detainee issue was key to ending the discord.
"You can't really have a serious political discussion if you haven't got all the players at the table," he said. "And keeping a bunch of them in prison just doesn't make sense under the present circumstances."
While the South Sudanese government seeks peace, it also has a duty to provide security in the country, Nhial Deng Nhial, the head of Kiir's delegation to Addis Ababa, said.
Kiir has declared an emergency in the oil rich Unity state and Jonglei region. That decision should be reversed, Gai said.
Bloomberg, ReutersAgence France-Presse