JUBA - South Sudan's army said Monday it was poised for a major offensive against rebel forces, as the country slid towards civil war despite international peace efforts.
Expectations of a major upsurge in fighting came as the United Nations warned that the situation in the world's youngest nation was fast unravelling, with hundreds of thousands of civilians now at risk.
Fighting has gripped South Sudan for more than a week, after President Salva Kiir accused his former deputy Riek Machar, who was fired from the government in July, of attempting a coup.
Machar denied the claim and accused Kiir of carrying out a vicious purge of his rivals. Vowing to oust Kiir, his forces have since seized the town of Bor, capital of the powder keg eastern Jonglei state and located just 200 kilometres (125 miles) north of Juba, as well as the town of Bentiu, capital of crucial oil-producing Unity state.
South Sudan army spokesman Philip Aguer said the government was on the offensive.
"Our soldiers will regain control of Bor town from the forces of the rebellion. The forces of Machar are still in control of the town, but we readying to take back control," he told AFP.
The comments came despite days of shuttle diplomacy by African nations and calls from the United States, Britain and the United Nations for the fighting to stop.
The UN's top humanitarian coordinator in South Sudan, Toby Lanzer, visited the besieged town of Bor on Sunday, and said the situation was rapidly deteriorating.
"It would have been have been difficult one week ago to imagine that things would have unravelled to this extent," Lanzer told AFP.
"There are hundreds of thousands of South Sudanese who've fled into the bush or back to their villages to get out of harm's way," he said.
Asked which areas of the conflict-torn country he was most concerned about, Lanzer said that "it would be quicker to talk about which areas I'm not worried about."
"I hope to be wrong, otherwise, hundreds of thousands will need help very soon," he said, adding he was "very concerned that a battle looms" in Bor, where he admitted that the UN peacekeepers were unlikely to be in a position to protect the estimated 15,000 civilians seeking shelter at the UN base there.
Hundreds killed, thousands fleeing
The clashes have left hundreds dead -- possibly many more -- and sent tens of thousands of people fleeing for protection in UN bases or to safer parts of the country, which only won independence from Sudan in 2011.
The young nation is oil-rich but deeply impoverished and awash with guns after the long war with Khartoum, and has grappled with corruption and lawlessness since independence.
There are both ethnic and political dimensions to the fighting, as troops loyal to Kiir, an ethnic Dinka, battle forces backing Machar, a Nuer.
Nuer gunmen stormed a UN base last week killing two Indian peacekeepers and slaughtering at least 20 Dinka civilians who had fled to the compound for shelter, and there have been reports of ethnically-motivated killings and attacks in the capital Juba and elsewhere.
Lanzer said the UN is "fortifying the camp in Bor, making sure there is no repeat of Akobo".
"But, as in Akobo, if there are few peacekeepers inside and 2,000 (fighters) outside, there's little we can do," he warned.
Foreign governments, including in Britain, Kenya, Lebanon, Uganda and the US, have been evacuating their nationals. On Saturday four US servicemen were wounded when their aircraft came under fire in a rebel-held area.
Britain is sending its third and final military aircraft on Monday to evacuate citizens, warning those who chose to stay "may have difficulty leaving in the event of a further deterioration in security".
UN peacekeepers have said they are also reinforcing their military presence in Pariang in oil-rich Unity state to help protect civilians. As in Bor, a top army commander in Bentiu switched sides to join the rebellion.
"The rebellion controls Bentiu... we are working on regaining control," army spokesman Aguer said.
Oil production accounts for more than 95 percent of South Sudan's fledgling economy, and the sector has been hit with oil companies evacuating employees after the death of at least five South Sudanese oil workers last week.
Juba's ambassador to Khartoum, however, insisted that oil facilities had not been damaged and oil was still flowing.
A local official in Bentiu said the area was littered with bodies following the fall of the town, and a witness from the area also said unidentified militiamen have been roaming the area for days, setting up road blocks and robbing passers-by.
The witness, who asked not to be identified, suggested fighters from nearby Darfur in Sudan may also have moved to the area to profit from the instability, adding there were unconfirmed reports of rapes.