South Sudan rebels loyal to fugitive former vice president Riek Machar have seized the key town of Bor, the army said Thursday, as fighting continued following an alleged failed coup bid.
"Our soldiers have lost control of Bor to the force of Riek Machar late on Wednesday," said army spokesman Philip Aguer.
"There was shooting last night... we don't have information on casualties or the displaced in the town, as operations are ongoing."
Bor, which lies some 200 kilometres (125 miles) north of Juba, is the capital of the eastern state of Jonglei, one of the most volatile regions in the young nation.
South Sudan President Salva Kiir has blamed Machar for organising a coup bid, with fighting breaking out late Sunday in Juba between army units.
But Machar, who was sacked by the president in July and is now on the run, has denied any coup attempt, and in turn accuses Kiir of using it as an excuse to purge his political rivals.
Machar, who fought on both sides during Sudan's 1983-2005 civil war, has been accused of leading a brutal massacre in Bor in 1991.
As fighting spreads outside the capital Juba -- now reported to be calm -- fears are growing in the international community of a return to civil war in the world's youngest country.
Powerful military commander Peter Gadet -- who rebelled in 2011 but then rejoined the army -- has also mutinied again, with his troops fighting pro-Kiir soldiers outside Bor.
"They are fighting in the bush," said Aguer.
However, security had been restored in Juba, he said.
"The situation in Juba is now back to normal, the streets are busy and shops are open," added Aguer.
Hundreds of people have been killed and thousands more terrified civilians have fled their homes to seek protection at UN bases since the fighting broke out on Sunday.
"Casualties in Juba are around 450 dead," said Aguer, adding that around a hundred of those were soldiers and the rest civilians.