Fighting erupted in South Sudan late on Saturday southwest of the capital between forces loyal to the president and the opposition, an opposition spokesman said, after fierce fighting last month in Juba raised fears of a slide back into civil war.
Witnesses reported heavy gunfire in the region around Yei, which lies on a road linking the capital Juba with neighbouring Uganda. There was no immediate comment from the government side.
Following the July fighting, the U.N. Security Council authorised the deployment of a 4,000-strong protection force to support the existing 12,000-strong U.N. peacekeeping mission.
Opposition spokesman James Gatdet blamed government forces for sparking clashes around Yei. "Our forces have managed to close Juba-Yei road. Our forces destroyed government's convoy that attacked our forces in the area," he said.
Each side regularly blames the other for any fighting.
Political differences between President Salva Kiir and his former deputy Riek Machar first erupted into conflict in late 2013. They signed a peace deal in August 2015, but sporadic fighting has continued.
Machar had recently returned to Juba to take up his position as deputy again when the July clashes flared. Machar then withdrew with his forces from the capital.
Kiir's spokesman Ateny Wek Ateny said after Friday's vote for extra U.N. troops that the government would not accept the new force, describing it as a U.N. bid to take over South Sudan.
The United Nations had threatened an arms embargo if the government did not cooperate.
It was not immediately clear if fighting around Yei had continued into Sunday morning. Residents in Juba said mobile phone communications to the area had been broken.
Regional states have backed sending extra troops to South Sudan in a bid to quell the conflict and prevent any further spillover. More than two million South Sudanese have been displaced by more than two years of conflict, and many fled to nearby states.
Kiir's cabinet is expected to meet later on Sunday.
