A spokesman for rebels in South Sudan says government troops are attacking their positions in a deliberate attempt to derail peace talks.
Brig. Lul Ruai Koang said on Sunday government troops are actively violating a cease-fire signed last week.
South Sudan military spokesman Col. Philip Aguer said he was unaware of fresh clashes.
Mr. Koang told the AP that rebel commanders report that government forces and allied militias attacked Leer town and surrounding villages in Unity state on Saturday, killing an unknown number of people. He said they also attacked rebel positions in Upper Nile state.
It was impossible to verify the allegations from Mr. Koang, who spoke in the Kenyan capital of Nairobi.
Leer is the town from which Doctors Without Borders reported fleeing on Friday with 240 hospital patients and workers.