At least 200 people have drowned in a ferry accident while fleeing fighting in South Sudan.

An army spokesperson says between 200 and 300 people - including women and children - on overloaded boats were caught up in the disaster.

He said they were fleeing fighting in the city of Malakal. It is believed no-one on board survived.

Rebel forces staged a fresh attack to seize the town, which has already changed hands twice since the conflict began on December 15th.

A United Nations peacekeeping base has been swamped by people seeking shelter, with numbers rising from 10,000 to 19,000.

Civilians fleeing the fighting & seeking refuge outside a UN compound in Bor (Image: UN Photo/Hailemichael Gebrekrstos)

Meanwhile UN food agencies are ramping up their relief efforts in the country, warning that the fighting there threatens to increase hunger and unravel the modest gains made in food security in the two years since the country seceded from Sudan.

The UN says a major concern is the displacement of some 355,000 people driven from their homes since the conflict erupted a month ago between President Salva Kiir's forces and those of former deputy president Riek Machar.

It says this threw the agricultural sector into turmoil at a time when preparations should be underway for plantings or harvests, "generating an alarming risk of food insecurity and malnutrition", according to the UN Food and Agriculture Organization (FAO).

Earlier this month, the UN released US$15 million from its rapid response fund for immediate humanitarian operations in South Sudan. But it has warned that even amid "very substantial progress", it could take up to eight weeks before the full 5,500-strong surge in UN peacekeepers and equipment is deployed on the ground.

Main image: UN Photo/Isaac Billy