The African Union has 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.
At a meeting in Gambia in West Africa, the AU said late on Monday it was dismayed by the bloodletting that has already killed more than a thousand people in the world's youngest country.
"(Council) expresses its intention to take appropriate measures, including targeted sanctions, against all those who incite violence, including along ethnic lines, continue hostilities (and) undermine the envisaged inclusive dialogue," the AU's Peace and Security Council said.
On Tuesday South Sudanese troops fought rebels believed to be loyal to former Vice President Riek Machar in the flashpoint town of Bor.
"We are fighting the rebels now," Mayor of Bor Nhial Majak Nhial told Reuters news agency.
South Sudan's neighbours have given the warring factions until the end of Tuesday to lay down their arms and begin negotiations - but so far there has been no sign of the hostilities ending.
The violence 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.
Ugandan President Yoweri Museveni said on Monday east African nations had agreed to move in and defeat rebel leader Riek Machar if he rejected a government ceasefire offer.
There was no immediate confirmation of the pact from other nations.
Even so, Museveni's words demonstrated the scale of regional worry over the fighting, often along ethnic lines between Machar's Nuer group and President Salva Kiir's Dinka, that has spread to South Sudan's oil fields, forcing a cut in output.