South Sudanese rebels have battled their way to the centre of the strategically important town of Bor and were in control of some neighbourhoods as the fighting raged on, the town's mayor and a government minister said.
"The town is still partly in our hands and partly in the hands of the rebels," Mayor Nhial Majak Nhial told Reuters on Tuesday.
Michael Makuei, Information Minister, said that rebels have advanced to the centre of town in South Sudan, and that fighting "is still taking place."
Earlier, Moses Ruai, a rebel spokesman, said that they have taken control of Bor. But that claim was dismissed by the South Sudanese military.
Al Jazeera's Mohamed Addow, reporting from Juba, said the fighting in Bor puts pressure on the government to negotiate with the rebels loyal to Riek Machar.
The army last week recaptured Bor from the rebel forces, who have been fighting government troops for over two weeks.
In recent days thousands have fled Bor - state capital of the Jonglei state, some 200 kilometres north of the capital Juba, fearing an impending counter-attack by rebels.
It was not immediately clear who was fighting in Bor, and whether it involved mutinous soldiers, who first seized the town and held it for a week before being driven out, or a loose militia force reported to have been marching on the town for days.
The South Sudanese government said on Tuesday they will send a delegation to Ethiopia for peace talks and the Ethiopian government said rebel leader Riek Machar would also send a team to the talks in its capital, Addis Ababa.
"We are going there," South Sudan Foreign Minister Barnaba Marial Benjamin told Reuters.
Benjamin also said President Salva Kiir will not share power with Machar because he had launched a coup against the country's leader.
On Tuesday the African Union threatened targeted sanctions against those inciting the violence in South Sudan and hampering international efforts to negotiate an end to the two-week outburst of fighting that risks drawing in the wider region.
Ugandan President Yoweri Museveni said on Monday east African nations had agreed to move in and defeat rebel leader Machar if he rejected a government ceasefire offer.
The violence first erupted on December 15 when fighting broke out among a group of soldiers in the capital, Juba, but quickly spread to more than half the country.
The conflict has left more than 1,000 dead in the past two weeks and displace over 180,000 people.