South Sudan army, rebels clash hours after ceasefire

South Sudan's army clashed with rebels in an oil-producing region early on Sunday, both sides said, shattering a ceasefire hours after it came into effect.The government and rebel groups signed a ceasefire on Thursday in the latest attempt to end a four-year civil war and let humanitarian groups reach civilians.The ceasefire formally came into force on Sunday morning, but fighting broke out soon afterwards, according to a humanitarian security report seen by Reuters.