"The UN secretary-general had a telephone conversation with President Museveni to see ways on how he can intervene in the current situation in Southern Sudan," Ugandan government spokesperson Ofwono Opondo told Anadolu Agency on Thursday. According to the UN News Center, the UN chief has discussed the dire situation in South Sudan with Museveni "because of his role as regional leader." "This is a political crisis and urgently needs to be dealt with through political dialogue. There is a risk of this violence spreading to other states, and we have already seen some signs of this," the UN chief asserted. South Sudan has been rocked by violence since Sunday, when President Salva Kiir said his forces had quashed an attempted coup led by sacked vice-president Riek Machar. On Thursday, security conditions in Bor, capital of Jonglei State, deteriorated significantly, with heavy fighting reported in the morning. The violence has prompted an exodus of civilians from Bor, with thousands seeking shelter at a UN compound located on the city's outskirts. On Wednesday, Machar denied involvement in the alleged coup attempt. In July, Kiir dismissed Machar – along with the entire government – and formed a special commission to investigate allegations of government corruption. Last year, Kiir had sent a letter to 75 current and former government officials suspected of embezzling some $4 billion worth of state funds.

-AU delegation-

Ugandan Foreign Affairs spokesperson Opolot Fred has confirmed that an African Union (AU) team was on way to South Sudanese capital Juba.

"The AU ministerial team has already been dispatched to South Sudan," he told AA.

"The meeting was very impromptu," Fred explained.

"The state minister for foreign affairs was in a meeting when he was asked to leave, but we'll get all the details when Addis avails it to us," he added.

Top diplomats from Ethiopia, Djibouti, Kenya and Uganda have already left Addis Ababa for Juba earlier this evening, well-placed sources with the Inter-Governmental Authority on Development (IGAD) told AA correspondent in Ethiopia.

All four countries are members of IGAD, an eight-country trade bloc based in Eastern Africa.

Ethiopia, Kenya and Uganda all share land borders with South Sudan.

Although the airport, main highways and official border points between South Sudan and Uganda have all been opened, the situation in Juba remains tense.

Buses that had been prevented from leaving Juba have now been allowed to set out.

On Wednesday, 14 buses arrived from Juba carrying 1,689 passengers, including 1,183 Ugandans.

The Ugandan government, meanwhile, has called on the public for any information regarding any Ugandan nationals killed in the South Sudan fighting.

"Unfortunately, there have been unverified reports of some Ugandan casualties," Opolot told AA.

"Anyone with verifiable information is kindly asked to notify the Ugandan embassy in Juba as soon as possible."