A ceasefire aimed at ending a brutal civil war in South Sudan came into effect Saturday evening hours after fresh clashes between government forces and rebels, which sparked concern for a hard-won peace deal.
The truce brokered by the regional eight-nation IGAD bloc, along with the United Nations, African Union, China, Britain, Norway and the United States, came into effect at 2100 GMT (midnight in South Sudan's capital Juba).
But it was unclear whether it would hold.
Earlier Saturday, South Sudan's army and rebels accused each other of sparking fresh fighting in the past 24 hours in the north-east.
"Riek Machar's rebels attacked Malakal yesterday (Friday)," army spokesman Colonel Philip Aguer told a press conference, referring to the capital of Upper Nile state, at the gateway to the country's last major oil fields.
Aguer said the rebels used mortars and machineguns and that one government soldier was wounded.
The "assault on Malakal resumed this (Saturday) morning," he said, insisting the army had a right to respond in self-defence.
Rebel spokesman James Gatdet Dak denied his camp had fired first.
"That's untrue, their forces attacked us near Malakal," he told AFP.
"They wanted to seize the area before the ceasefire comes into effect," he added.
"This is a serious violation of the terms of the peace agreement," a rebel statement charged -- an accusation echoed on the government side by information minister and government spokesman Michael Makuei.
A peace deal signed by rebel leader Machar on August 17, but only signed by President Salva Kiir on Wednesday, gave a 72-hour deadline for a permanent cessation of 20 months of hostilities.
Aguer, the army spokesman, called on IGAD to establish a ceasefire monitoring mechanism "in all the counties".
But IGAD spokesman Hailemichael Gebreselassie denied any knowledge of the latest clashes, saying: "We haven't heard anything related to any incidents."
South Sudan broke away from Sudan four years ago to become the world's newest nation.
The civil war began in December 2013 when President Kiir accused Machar, his former deputy, of planning a coup, setting off a cycle of retaliatory killings that has split the impoverished country along ethnic lines.
Faced with the threat of international sanctions, Kiir finally signed the peace deal this week but annexed a list of reservations that he said would have to be addressed for the deal to take hold.
Machar said the reservations cast "doubts" on the government's commitment to peace.
The UN Security Council on Friday threatened sanctions against anyone who undermined the accord.
The agreement gives the rebels the post of first vice president, which means that Machar would likely return to the job from which he was sacked, an event that put the country on the path to war.
The 12-page list of government reservations on the peace deal says his return would spell "humiliation" and a "reward for rebellion".
At least seven ceasefires have already been agreed and then shattered within days or even hours.
Over two million people have fled their homes in a conflict marked by ethnic killings, gang rapes and the use of child soldiers. Some 200,000 civilians are sheltering inside UN bases.