Rebels in South Sudan say government forces are attacking their positions, one day after a cease-fire was signed.

Brig. Gen. Lul Ruai Koang, a spokesman for the opposition, said Friday that government forces were attacking rebel positions in oil-rich Unity state and in Jonglei state.

Koang called the attacks a "clear violation" of the peace deal signed in Ethiopia on Thursday. He said rebel forces would defend themselves against attacks.

In South Sudan, military spokesman Col. Philip Aguer said he is not aware of any new violence but said there was fighting in Jonglei on Thursday. Aguer said if new fighting has occurred "it is because rebels have attacked" government soldiers.

Fighting broke out on Dec. 15 in the world's newest country, killing thousands of people.