South Sudan's army and rebels have both stepped up the kidnapping of children to fight in the country's civil war, with hundreds snatched from villages in the last month alone, the UN children's agency has said.

Providing the most detailed account yet of the country's child soldier crisis, UNICEF said in a statement on Friday that it believed there were now more than 12,000 children in government and rebel ranks across the country.

"It has become increasingly desperate for boy children in many areas of the conflict zone. They are being targeted. They are being rounded up and sent to the front line. This is happening as I speak," Jonathan Veitch, UNICEF's representative in the country, said.

Veitch said UNICEF had "credible and in some instances verifiable information that forces aligned with the government and opposition have abducted or coerced hundreds of children into their ranks in the past month
alone", a period coinciding with the collapse of peace talks.

"Our teams on the ground and our partners are reporting a strong upsurge in recruitment at the moment and it is ongoing," he told reporters in Geneva.

South Sudan is the the world's youngest nation, having broken away from Khartoum in 2011 after a long and bloody independence struggle.

Civil war broke out in the new nation in December 2013, when President Salva Kiir accused Riek Machar, his former deputy, of planning a coup. Since then tens of thousands have died, two million have been uprooted and four million face starvation.

The government and the rebels have been accused of widespread atrocities and war crimes - including gang rapes, massacres and attacks on aid organisations and peacekeepers.

Earlier this month the UN Security Council passed a US-drafted resolution creating a sanctions regime for South Sudan, although none have yet been imposed.

Veitch reminded South Sudan's warring factions that the resolution "specifically lists the recruitment of children as soldiers as one of the criteria for imposing sanctions".

The comments came after both the government and the rebels signalled clearly that they were in no mood for peace following the collapse of talks in Ethiopia's capital Addis Ababa.

On Thursday, the rebels said the civil war would likely drag on and that "fighting will continue until one side is defeated". President Kiir earlier this week also ruled out sharing power with Machar, rejecting key elements of peace deal proposed by regional mediators.

Source: Agencies