JUBA - More than 60 people have been killed in Sudan's disputed region of Abyei over the past three days in a series of clashes involving local Ngok Dinka police forces and militias allegedly associated with the nomadic tribe of Mesiria, a senior official of the Abyei Referendum Forum (ARF) told Xinhua on Monday.

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The casualties included about 40 from Mesiria and 24 Ngok Dinka civilians in the clashes from Friday to Sunday, ARF acting Chairman Deng Mading said, noting "we are getting more reports of casualties as the fights are going on."

The Dinka forces captured two tanks in the color of the UN peacekeepers from the enemies on Saturday and handed them over to the southern army Sudan People's Liberation Army (SPLA), he said, adding "we were checking the identity of the tanks."

Reports over the cause of the violence are not clear with different reasons put forward from both sides.

Senior Mesiria leader Hamdi al-Doudo was reported by Sudan Tribune as saying that the clashes were triggered by the SPLA moving up to 1,500 soldiers into the area, which the Arab nomads regarded as a route to grazing fields.

But Mading said the alleged reasons are "absolutely not right," telling Xinhua that "actually, the invading forces are moving 3,000 troops to Abyei," he told Xinhua.