JUBA, Sudan - Soldiers in north Sudan's army fought each other, killing at least 30 in a dispute over who gets to keep the artillery they are holding in Southern Sudan, officials said Sunday.

The fighting took place Saturday in two towns in Upper Nile state between soldiers of the Sudanese Armed Forces, said Akuoc Teng Diing, the county commissioner of Melut where some of the conflict took place. Diing said soldiers also fought each other in Paloich, nearly 150 kilometres northeast of Upper Nile state's capital, Malakal. Paloich is the site of the most productive oil fields in Sudan. Some 300,000 barrels of oil are pumped daily from the fields.

Diing said that 11 soldiers were killed in Paloich and 19 in Melut. He said most of the soldiers in the Sudanese Armed Forces unit are southerners who had fought on the side of the north during the 21-year war between the north and south.

"The cause of the fighting is the same as that of Malakal," wrote Upper Nile State Information Minister Peter Lam Both in a Saturday e-mail seen by The Associated Press. Both was referring to two days of fighting in Malakal over the past week during which a separate group of soldiers turned on each other.

Both said that one camp of Southern Sudanese men within the northern military wants to "keep their artilleries in South(ern) Sudan because they were given to them during the war."

On Thursday and Friday, a separate unit of Sudanese Armed Forces soldiers fought each other, with initial reports saying nine died. Under a 2005 peace deal that ended the north-south Sudan war, both regions are allowed to keep separate armies. That deal also allows the north to keep some units in the south.

Col. Philip Aguer, spokesman for Southern Sudan's military, the Sudan People's Liberation Army, said Saturday that the death toll from the fighting in Malakal rose to more than 20.

The Sudanese Armed Forces, the military of the north, keeps units in Southern Sudan. They will be expected to move back north if preliminary referendum results showing strong support for the south to secede are confirmed.

The pullback of the Sudanese Armed Forces is not expected to begin until April. But Aguer said the latest fighting has brought forward such plans for the troops in Upper Nile State.

Southern Sudan announced Jan. 30 that 99 per cent of voters in the south voted for independence during a referendum earlier in January.

Southern Sudan is slated to become the world's newest country in July. The independence referendum was guaranteed in the 2005 peace accord.