* At least 45 dead in four-day offensive
* Rebels pledge to continue "until victory"
By Jeremy Clarke
JUBA, Sudan, April 22 (Reuters) - Several soldiers were killed in clashes between south Sudan&${esc.hash}39;s army and rebel militia in oil-producing Unity State, the army said on Friday.
Ahead of independence in July, analysts have warned south Sudan must maintain security to avoid becoming a failed state and destabilising much of the region.
At least seven rebel militia are fighting the southern army (SPLA) across Sudan&${esc.hash}39;s south, where more than 800 people have been killed this year from the clashes and traditional tribal conflicts, the United Nations has said.
The south voted to separate from the north and form a new African nation in a January referendum that was promised to them as part of a 2005 peace deal that ended decades of civil war in Sudan, which claimed at least two million lives.
The fourth day of an offensive in the south&${esc.hash}39;s Unity State by a rebel militia group led by former SPLA officer Peter Gadet claimed "many more" lives on Friday when wounded SPLA soldiers were ambushed, SPLA spokesman Philip Aguer told Reuters.
"It was an unarmed convoy transporting wounded SPLA soldiers that came under attack, many more were killed," Aguer said. He could not immediately give the exact number.
"They came first on April 18 and laid landmines, the attacks then started on the 19th," he said.
Bol Gatkouth Kol, who identified himself as a spokesman for the rebels, said the offensive would continue "until victory".
"Our forces are doing a tremendous job ... the next stage is moving on to Bentiu," Kol said, referring to the capital of Unity State.
Kol said the rebels had lost 12 fighters so far, which would take the death toll to at least 45 since the clashes began this week, excluding the SPLA soldiers killed on Friday.
The toll includes 20 SPLA soliders, 11 Misseriya tribesmen that the southern army says is fighting alongside Gadet, and two civilians who ran over landmines in trucks.
The southern army said Gadet is leading a coalition force after recruiting fighters from the northern Misseriya tribe, which Kol and the Misseriya deny. Both say they are operating alone.
The rebels accuse the southern government of corruption and nepotism while neglecting development, Kol said.
In response to the clashes in Unity State this week, state officials expelled northern Sudanese who were working in oil areas before agreeing to readmit them a day later, underscoring the threat instability poses to oil production.
Output at the Unity oilfields, which produce 84,000 barrels per day, was disrupted by the expulsion because most of the 212 workers there were north Sudanese, according to officials.
Oil is the lifeblood of the northern and southern economies and the two governments have yet to work out how to share the revenue from southern oil after separation. The south is the source of most of Sudan&${esc.hash}39;s 500,000 barrels per day of oil.
At present, revenue from southern oil is spilt roughly 50-50 between south and north, and the south will have to rely on pipelines in the north after July.
The south has fought the north for all but a few years since 1955 over differences in religion, ideology, ethnicity and oil. (Editing by Deepa Babington)
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