* Ceasefire agreed on Thursday after weeks of fighting
* Violence since mid-December has killed thousands
By Carl Odera
JUBA, Jan 25 (Reuters) - The government and rebels in South Sudan traded accusations on Saturday of breaking a ceasefire deal supposed to calm violence that has driven half a million people from their homes.
"The rebel forces are still continuing to attack our forces," Information Minister Michael Makeui Lueth said on arrival from Ethiopia where President Salva Kiir's government signed a deal on Thursday with the rebels led by former vice president Riek Machar.
The deal came into effect on Friday night after a 24-hour window under an agreement brokered by regional grouping of nations IGAD.
"If nothing is done by the IGAD, then definitely our forces will not fold their hands," Lueth said.
A rebel spokesman accused the government of launching attacks on their positions in Unity, Jonglei and Upper Nile states soon after the agreement was signed.
"For them to turn around and accuse us is ridiculous," Lul Ruai Koang told Reuters in the Kenyan capital Nairobi.
IGAD's mediators were not immediately available to comment.
The rebellion, which broke out in Africa's newest state mid-last month, has pitted Kiir's troops against those loyal to Machar as well as more autonomous groups.
Lueth suggested that could be why rebel soldiers were still carrying out attacks, since they lacked a unified command.
"Rebels are indisciplined people. They have no regular force. They have no central command. In that case, it's not strange that they immediately violate (the agreement)," the minister said.
Koang rejected the claim.
"We do not have factions. We have one central command. It is the government that has three commands," he said, citing the tribal army under the control of the president, the national army and the Ugandan troops who have been fighting alongside the government.
Although initially caused by a political row, the conflict has taken a tribal turn with Kiir's Dinka clashing with Machar's Nuer. Thousands of people have been killed.
A Reuters journalist in the town of Bor, to the north of the capital, heard shelling at lunchtime on Saturday and saw two government soldiers who had just been wounded in the fighting.
"This is clearly a violation of the cessation of hostilities," Malual Ayom, a government army commander told reporters in Bor.
South Sudan gained independence from Sudan to the north in 2011 after decades of war between both sides.