South Sudan's information minister says rebels in the country are attacking positions held by government troops, putting into question the strength of a recently signed cease-fire.

Michael Makeur Lueth said Saturday that rebel fighters are violating the peace deal signed Thursday in Ethiopia and that if attacks don't stop government forces will defend themselves.

Lueth declined to say where the attacks were taking place. Fighting took place in Jonglei state on Friday. Government officials have previously expressed doubts that rebels in Jonglei known as the White Army would abide by the deal. Lueth called rebel fighters "undisciplined people" without a central command.

South Sudan's conflict broke out Dec. 15 and has since killed thousands of people. An estimated half million people have been displaced.