JUBA- Rebels in South Sudan attacked towns in two states on Tuesday, the army said, barely a week after signing another ceasefire agreement with the government that was meant to end 15 months of conflict.Thousands of people have been killed and more than a million have fled their homes since fighting erupted in the world's newest nation in December 2013, triggered by a power struggle between President Salva Kiir and former vice president Riek Machar.Philip Aguer, spokesman for South Sudan's army, the SPLA, said the attacks had occurred in the capital of oil-producing Unity state Bentiu and in Upper Nile State, both in the north of the country."A ground attack was launched by the rebels in Upper Nile today on SPLA positions in Obudo County using a big force supported by heavy machine guns," Aguer told Reuters."Another area of violation by the rebels was in Unity state. The rebels shelled SPLA force positions in Bentiu north of the town this morning."He gave no details of casualties and said the SPLA had repulsed the rebels and captured two vehicles and heavy machine guns. Aguer added that fighting was still raging in Upper Nile.The rebels were not immediately reachable for comment.