Some 700,000 people have already been affected by what seem set to become the worst floods in 60 years in South Sudan, the United Nations said Tuesday.

"The humanitarian situation is worsening," Matthew Hollingworth, the World Food Programme's South Sudan country director, told a virtual briefing in Geneva.

"About 700,000 people are in dire straits as unprecedented flooding sweeps across the country, submerging whole villages, homes, farmlands, livestock and livelihoods."

Of the total number of people affected, 230,000 are in Jonglei, the worst-affected state, and have experienced flooding incidents more than once. Some 85,000 people have been displaced.

"What is of serious concern is these torrential rains we are witnessing have started before the water from last year's flooding fully receded," said Hollingworth.

"Now, in 2020, the flooding is likely to be more severe, the worst in 60 years -- and we are not yet at the peak of the annual flood season."

In Jonglei, more than 1.4 million people are suffering from acute and severe hunger.

"These difficult conditions are bound to deteriorate further if no adequate humanitarian assistance is provided," said Hollingworth.

The United Nations' World Food Programme is aiming to support the 700,000 flood-affected people and needs at least $58 million for the coming six months to deliver emergency life-saving food assistance to alleviate hunger and malnutrition.

It also said it would work to reduce the risk of future flooding disasters by rebuilding dykes.

South Sudan is struggling to cope with the aftermath of a six-year civil war that killed around 380,000 people and crippled output of crude oil, which accounts for more than 90 percent of state revenue.

An earlier report from the UN humanitarian office OCHA said that 7.5 million people across South Sudan needed humanitarian aid, of which 6.5 million are going hungry.