South Sudan rebels on Sunday accused the army of violating a ceasefire, just hours after it came into effect, by bombarding their positions along the White Nile river.

South Sudan rebels on Sunday accused the army of violating a ceasefire, just hours after it came into effect, by bombarding their positions along the White Nile river.

"A military convoy -- two barges, seven gunboats -- has been moving from Bor to Panijar. Whenever they see our positions on the banks, they shell," said rebel spokesman Dickson Gatluak.

"The cessation of hostilities started at midnight on Saturday butthe government has broken it. They are not committed to it," he added.

The spokesman added that the rebels would on Monday report the situation to the regional eight-nation IGAD bloc which helped broker the pact.

Neither the South Sudanese government nor the army were immediately available for comment.

President Salva Kiir on Wednesday signed a peace accord, already signed by the rebel chief Riek Machar.

The ceasefire aimed at ending a brutal civil war in South Sudan came into effect on Saturday evening, hours after fresh clashes between government forces and rebels, which sparked concern for the hard-won peace deal.

The truce brokered by the IGAD bloc, along with the United Nations, African Union, China, Britain, Norway and the United States, came into effect at 2100 GMT (midnight in South Sudan's capital Juba).

On Saturday, South Sudan's army and rebels accused each other of sparking fresh fighting in the preceding 24 hours in the north-east.