JUBA: South Sudan rebels Sunday accused the army of violating a cease-fire 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,” rebel spokesman Dickson Gatluak said.

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

The army immediately denied the rebel claims.

“First of all, there is no [army] force operating in that area,” army spokesman Philip Aguer said.

“These are mere fabrications by the rebels. We don’t have any report of clashes in that area as of today,” he said.

“As we said, we want IGAD to station monitors in all the counties so as to monitor and see who is violating the cease-fire instead of us answering to the international media on fabrications by the rebels.”

IGAD has so far been unable to independently verify the claims and counteraccusations.

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

The cease-fire aimed at ending a brutal civil war in South Sudan came into effect 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 21:00 GMT Saturday.

On Saturday, South Sudan’s army and rebels accused each other of sparking fresh fighting in the preceding 24 hours in the northeast.

At least seven cease-fires have already been agreed and then shattered within days or even hours in the world’s youngest nation.

Over 2 million people have fled their homes in a 20-month conflict marked by ethnic killings, gang rapes and the use of child soldiers. Some 200,000 civilians are sheltering inside U.N. bases.

The civil war began in December 2013 when Kiir accused Machar, his former deputy, of planning a coup, setting off a cycle of retaliatory killings that has split the impoverished country along ethnic lines.

Faced with the threat of international sanctions, Kiir finally signed the deal but annexed a list of reservations that he said would have to be addressed for the deal to take hold.

Machar has said the reservations cast “doubts” on the government’s commitment to peace.

The U.N. Security Council Friday threatened sanctions against anyone who undermines the accord.

The agreement gives the rebels the post of first vice president, which means that Machar would likely return to the job from which he was sacked, an event that put the country on the path to war.

The 12-page list of government reservations on the peace deal says his return would spell “humiliation” and a “reward for rebellion.”