|Rebel fighters and the Sudan Peoples Liberation Army both blame each other for the latest violence [EPA]
At least 105 people have been killed in a spate of clashes between rebels and the south Sudanese army, days after results of a referendum on independence in the region.
The violence, which began when fighters loyal to rebel leader George Athor attacked an army base in Jonglei state earlier in the week, breaks a ceasefire signed last month.
"There were 39 civilians killed, including women and children, and 65 others wounded," Philip Aguer, an army spokesman said.
The military said fighting at Fangak in Jonglei on Wednesday and Thursday had killed 50 fighters from both sides, adding to the 16 casualties it reported a day earlier from violence in Door.
"The number of casualties is high because the attacks were a surprise. This is something we were not expecting because we trusted the ceasefire that was signed," the AFP news agency quoted Aguer as saying.
Athor, speaking on Sudan Radio Service, blamed the south Sudanese army, formerly the Sudan People's Liberation Army (SPLA), for starting the attacks.
The rebel leader began fighting last year after saying he was cheated in an election for the governorship of Jonglei, the south's most populous state. But in January his men signed a ceasefire with the SPLA.
Southern officials have accused him of using the ceasefire period to recruit more fighters.
This week's attacks also come days after the official results of a referendum for independence in southern Sudan were released, showing a nearly 99 per cent landslide in favour of secession.
Analysts have said that maintaining security in the fledgling southern nation, which is due to win international recognition in July, will be a major challenge.
Clashes in oil-producing Upper Nile state earlier this month killed 54 people and wounded 85, according to UN estimates, when southern fighters inside the northern army rebelled against orders to surrender their heavy weapons.
A south Sudan minister was shot dead in his Juba office on Wednesday, adding to fears of instability in the region.