NAIROBI (Reuters) - Violence in South Sudan is blocking deliveries of food aid needed to stave off severe hunger in some areas, the World Food Programme said, adding to evidence that a peace deal signed last month is not holding.

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The deal signed last month is meant to end a war that began in 2013 and has, according to a London School of Hygiene and Tropical Medicine study, killed nearly 400,000.

It commits the warring parties -- forces loyal to President Salva Kiir and rebel groups fighting them -- to power-sharing. Analysts and aid groups say it is unclear how the structure will work.

Fighting was continuing in the Western Bahr el Ghazal and Central Equatoria regions, said WFP. Nationwide “tens of thousands of people (are) in need,” the group’s Country Director Adnan Khan told Reuters by e-mail.

WFP singled out Baggari, an area southwest of the city of Wau, in Bahr el Ghazal, where the severity and spread of hunger was alarming.

“Food distributions were briefly provided in September, after four months without access, but insecurity is again preventing us from accessing the area,” it said.

When it was able to briefly access Baggari last month, WFP found acute malnutrition rates had risen to above 25 percent from 4 percent earlier this year.

In Wau, government soldiers have been accused by Human Rights Watch of attacking civilians and their homes.

“Tens of thousands of people have been forced to flee into the bush or United Nations protection sites,” HRW said last week in a report on violence that began in June. “...Government forces are committing new abuses against civilians.”

Military spokesman Lul Ruai Koang denied the HRW report’s findings.

The East African nation gained independence in 2011 but has been torn apart by an ethnically charged civil war since late 2013.

On Wednesday, rebel leader Riek Machar is due to fly from Sudan’s capital Khartoum to Juba for a “Peace Celebration” hosted by Kiir and that the presidents of Sudan, Uganda and Kenya are expected to attend.

It is unclear if Machar will be there. On Friday a spokesman for his group said: “We are still waiting for the release of political detainees and prisoners of war”.

Machar was last in South Sudan was in 2016, after he was reinstated vice president under a short-lived peace deal agreed in 2015.