South Sudan’s army and anti-government rebels have both accused one another of violating a ceasefire just hours after it came into effect.

The peace agreement, in place since 00:01 local time on Sunday, was brokered earlier this week after days of internationally mediated talks in neighbouring Ethiopia to allow for humanitarian aid to get to civilians caught up in the fighting.

It marked the latest attempt to end a devastating civil war that began in 2013 when forces loyal to President Salva Kiir started fighting those allied to his former deputy, Riek Machar.

However, a spokesman for Machar’s SPLA-IO group said in a statement on Sunday that rebel bases in the north of the country had come under "the most aggressive attack” earlier in the day.

Lam Paul Gabriel said the group’s fighters had "repulsed” an attack by government troops in northern Koch County.

He added that SPLA-IO positions in southwestern Yei County were being bombarded and accused the military of sending in soldiers to attack rebel bases in the western Wau region.

"These are all acts against the peace process as the government in Juba wants the SPLA-IO to respond so that war continues and they continue to loot the resources of the country,” said Gabriel.

Speaking to Al Jazeera, Lul Ruai Koang, a spokesman for the army, denied the allegations.

"It’s actually the opposite … The rebels violated the ceasefire today in Koch,” he said by phone.

Koang accused the SPLA-IO of instigating the attacks in Koch, adding that government troops regained control of the Bieh Payam town in the area by afternoon.

There were no clashes in the country late on Sunday, he said.

Koang also accused the armed opposition’s forces of ambushing an aid convoy in southern Amadi state on Saturday.

"The fighting is an indication that the rebels are not in full control of their troops,” Koang said, adding that the government would continue to respect the truce.

Humanitarian crisis

South Sudan’s warring sides agreed on Thursday in Ethiopia’s capital, Addis Ababa, to end hostilities and "immediately freeze in their locations”.

They also said they would grant unhindered access for aid workers to all areas and release all political detainees as well as abducted women and children.

South Sudan plunged into civil war just two years after gaining independence when Kiir accused Machar, who he had sacked earlier in 2011, of plotting a coup.

The clashes that followed between forces loyal to Kiir - who is from the Dinka ethnic group - and rebels allied to Machar - a Nuer - set off a cycle of retaliatory killings that have split the world’s newest country along ethnic lines.

A peace accord was signed two years later, and Machar returned to the capital in April 2016 to share power with Kiir.

The deal, however, collapsed in July and violence broke out. Machar went into exile and the fighting continued with new armed opposition groups joining the war over the past year.

The conflict has resulted in tens of thousands of people being killed and a quarter of the country’s 12 million population forced from their homes

According to the UN, six million people - half of the country’s population - are in desperate need of humanitarian assistance.

More than 1.2 million are at risk of famine if humanitarian assistance is not delivered by next year.

South Sudan won independence from Sudan in 2011.

Agencies