A South Sudan army general has been killed in fighting outside the rebel-held town of Bor.
A BBC correspondent with government troops said a convoy advancing on Bor came under heavy fire in an ambush.
The general - who has not been named - was killed.
Army units loyal to President Salva Kiir have been fighting rebel forces under former deputy President Riek Machar since 15 December.
Substantive talks between their factions are due to start on Sunday in Ethiopia. A preliminary meeting was held on Saturday.
The BBC reports fighting is also continuing in the oil-producing states of Unity and Upper Nile in the north. The rebel foreces include former army units.