The sacks of grain falling from the sky are the first food aid the people of Dablual have seen in months since fighting cut the South Sudanese village off in April.

Here in the northern battleground state of Unity, fighting in South Sudan's 19-month civil war has escalated since April, with government and rebel forces accused of burning people alive, gang rape and recruiting large numbers of child soldiers.

"We want peace, we are really suffering... anytime they can come, kill children, rape the women, burn the children -- those in the houses they burnt them alive," said David, recounting what government forces did when they attacked his village of Koch.

People here survived by retreating into the rebel-held enclave then fishing in rivers or gathering water lilies from the swamps. Their farms have been destroyed, livestock stolen and grain stores ransacked.

Scores of their neighbours were killed in the fighting, they say, while others died of disease, sickness or hunger.

"Life is very bad, my cows were all taken by government forces. Here there is no food at all," said David, one of around 30,000 people here who fled intense fighting to this remote and already hugely overstretched village.

"The food security situation is alarming," according to the United Nations with "nearly 70 percent" of the country's population -- 7.9 million out of 11.6 million people -– expected to face hunger during the current rainy season.

South Sudan's civil war began in December 2013 when President Salva Kiir accused his former deputy Riek Machar of plotting a coup, setting off a cycle of retaliatory killings that has split the poverty-stricken, landlocked country along ethnic lines.

Tens of thousands have died in the war, according to the UN, but no official death toll has been kept.

Pressure is once again mounting on the warring leaders to strike a deal.

- From joy to despair -

US President Barack Obama, who wrapped up a two-nation Africa tour Tuesday, has focused attention on South Sudan, holding talks with regional leaders in Ethiopia and raising the issue in an address to the African Union.

"The joy of independence has descended into the despair of violence," Obama said of Africa's newest nation which broke free from Sudan in 2011.

"Neither Mr Kiir not Mr Machar have shown any interest in sparing their people from this suffering or in reaching a political solution," Obama said. He promised to "raise the costs of their intransigence" if a regionally imposed August 17 deadline for a peace agreement is not met.

Despite so far failing to halt the fighting, the east African regional bloc IGAD remains the best bet for a peace deal, analysts say.

"The coming weeks will require concerted international action, coordinated with IGAD, to take the final, necessary steps to secure an agreement," the International Crisis Group (ICG) think tank said in a report Monday.

The group described the initiative as "the last, best chance for peace".

For those struggling for survival in the swamplands of Dablual, an end to fighting cannot come soon enough.

"The government took away all my cattle and burnt my houses, and killed some of my relatives," said Nayluak, a mother of seven who depends almost entirely on UN handouts to survive.

"I call on the government and the rebels to sign for peace and end our suffering," she said.

In Dablual, World Food Programme (WFP) planes -- too big to land in the swamplands here -- made their first drop for months. WFP country chief Joyce Luma called the situation "desperate".

The UN has warned of a "humanitarian catastrophe", with this area just one step away from famine.

At the end of a four-day visit last week UN aid chief Stephen O'Brien spoke of the enormous struggles of ordinary South Sudanese he had met.

"They have lost husbands, wives and children. Their homes and livelihoods have been destroyed," said O'Brien. "Women and girls have been targeted throughout the conflict, they have been beaten, abducted, raped and set on fire."