U.N. Secretary-General Ban Ki-moon on Tuesday accused South Sudan's army and rebels led by former Vice President Riek Machar of stealing food aid and vehicles used to deliver humanitarian relief as the country teeters on the brink of civil war.
"(Ban) is alarmed by the rising number of fatalities resulting from the continuing fighting in South Sudan, including reports received on 14 January about the deaths of 200 civilians who drowned in the River Nile while fleeing hostilities in Malakal," the U.N. press office said.
A government spokesman said the people died as they took to the river to flee clashes in Malakal, a major transit point and administrative center of Upper Nile state.
"(Ban) strongly condemns the commandeering of humanitarian vehicles and the theft of food stocks and other relief items by both Government and anti-Government forces," Ban's press office said in a statement.
The statement said Ban was also deeply concerned about the rising number of displaced people in South Sudan, which he said surpassed 400,000 this week.
The crisis erupted after South Sudan President Salva Kiir fired Machar and other ministers earlier this year. Machar's rebels are demanding the release of 11 of their political allies jailed after they were accused of attempting a coup.
Fighting that erupted in mid-December has reopened ethnic faultlines. According to one estimate, the conflict may have killed as many as 10,000 people, although there is no official toll for those killed in the desperately poor nation.
The United Nations has said that well over 1,000 people have died.
The United States is weighing targeted sanctions against South Sudan due to the failure of leaders in the world's youngest nation to take steps to end a crisis that has brought the country to the brink of civil war, sources briefed on U.S. discussions told Reuters last week.
South Sudan split from Khartoum in 2011 as part of a 2005 U.S.-backed peace deal that ended decades of civil war.