South Sudan's armed opposition is accusing government troops of violating a cease-fire just hours after it came into effect.

A statement by opposition spokesman Lam Paul Gabriel says government troops have been "bombarding" opposition positions in Yei county and launched an attack in Koch county Sunday morning that opposition forces "repulsed."

These are the first reported violations of the cease-fire that went into effect just after midnight. The warring sides agreed to the cessation of hostilities on Thursday after days of internationally mediated talks.

South Sudan government spokesman Ateny Wek Ateny tells The Associated Press that "How can we violate the cease-fire? It just went into effect. ... We can only fire back in self-defense."

The East African country is entering its fifth year of civil war.