United Nations, Jan 15 (IANS): UN Secretary-General Ban Ki-moon has said he is "alarmed" by the climbing toll in South Sudan since the fighting broke out a month ago between anti- and pro-government forces.

A statement issued here Tuesday said Ban "is alarmed by the rising number of fatalities resulting from the continuing fighting in South Sudan", including the deaths of more than 200 civilians who drowned in the Nile river while fleeing hostilities in Malakal, capital of the Upper Nile state in South Sudan, Xinhua reported.

"He is also deeply concerned about the rising number of displaced people in the country, which surpassed 400,000 this week, and the challenges humanitarians are facing in providing life-saving assistance," the statement said.

At least 250 people drowned Sunday as they were travelling on a boat from Malakal to flee alleged attacks by forces of former vice-president Riek Machar on the town.

During the past few weeks, the world's youngest country has witnessed clashes between two military factions, one descending from the Dinka tribe, to which South Sudan President Salva Kiir Mayardit belongs, and the other descending from the Nuer tribe, to which Machar belongs.

The two sides have been negotiating in the Ethiopian capital Addis Ababa under the patronage of the Inter-Governmental Authority for Development. The two sides have so far failed to reach an agreement on ceasefire.

Ban called on all parties to end hostilities and urged them to engage constructively in the negotiation process.