KHARTOUM, Jan. 13 -- At least 250 people have drowned as they were travelling on a boat from Malakal, capital of the Upper Nile State in South Sudan, to flee alleged attacks by forces of ex-vice president Riek Machar on the town, Upper Nile State's information minister told Xinhua by phone on Monday.

"The boat drowned with about 255 people on board. Only two children have been rescued," said Upper Nile State's information minister Philip Jiben.

"The boat was carrying those people who tended to flee from Malakal town after incorrect news were circulated that Machar's forces were attacking the town," he added.

He reiterated that the situation in Malakal was calm, refuting media reports that Machar forces attacked Malakal and seized some parts of it.

"No attack was launched against Malakal. The town is completely calm and the life is progressing naturally. There is no any fighting at any part of the town," noted Jiben.

During the past few weeks, South Sudan 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 (IGAD). The two sides have failed so far to reach an agreement on ceasefire.

The rebels' leader Machar insists on the release of 11 political and military detainees who have been accused of planning an alleged military coup against South Sudan government, while Juba insists that it would not release them until the investigations with them are over.

The Ethiopian member of the IGAD mediation team Seyoum Mesfin was reported to have said the mediation proposed to Kiir to release the detainees to participate in the negotiation process, provided that they were to be under the custody of the United Nations and the IAGD.

According to Ashrouq news, Mesfin said Kiir has expressed readiness to consider all options to resolve that matter.