The UN's World Food Programme on Tuesday appealed for $426 million to stave off famine in South Sudan, where conflict and floods have placed millions at risk.

"We are already in a crisis, but we need to restore food assistance... to prevent people from falling into starvation and famine. To do so, we urgently require $426 million for the next six months," WFP's programme officer for South Sudan, Adeyinka Badejo, told reporters.

"South Sudan is facing its hungriest year since independence," Badejo warned from the capital Juba.

The reasons, she said, were accumulative -- "continuing sub-national conflict, climate crisis of three consecutive years of floods, and severe economic shocks exacerbated by the Covid-19 pandemic, and now the war in Ukraine."

The youngest country in the world, South Sudan has experienced chronic instability since becoming independent from Sudan in 2011.

A civil war between 2013-2018 left nearly 400,000 dead and millions displaced. 

A peace accord provided for a power-sharing arrangement in a unity government gathering the two rivals, President Salva Kiir and Vice President Riek Machar.

But many articles of the accord are still to be implemented and armed clashes between the two sides have resumed.

Amplifying the impact from violence has been flooding.

The impoverished landlocked country is bracing for a fourth successive year of floods that could force 600,000 people from their homes, said Badejo.

Last year a million people were displaced.

"More than two-thirds of the population are experiencing a serious humanitarian and protection crisis and require humanitarian assistance to survive," she said. 

"Of these, we estimate that 8.3 million people, including internally displaced persons and refugees, will endure severe acute hunger during the lean season. This also includes two million women and children at risk of acute malnutrition in 2022."

This year, the WFP had planned to provide food assistance to 6.2 million people.

But mounting demands and insufficient funds meant that the agency in April had to suspend help for 1.7 million of these -- people deemed to be in relatively lower categories of food insecurity.