JUBA, South Sudan (AP) — Gunmen attacked villagers in the oil-rich region of Abyei claimed by both Sudan and South Sudan, leaving at least 52 people dead, including a U.N. peacekeeper, and 64 wounded, a regional official said Sunday.

The motive for the attack Saturday evening was not immediately clear but it was suspected to revolve around a land dispute, Bulis Koch, Abyei information minister, told The Associated Press in a telephone interview from Abyei.

Deadly ethnic violence has been common in the region, where Twic Dinka tribal members from neighboring Warrap State are locked in a land dispute with Ngok Dinka from Abyei over the Aneet area, located at the border.

The attackers in Saturday’s violence were armed youth from the Nuer tribe who migrated to Warrap state last year because of flooding in their areas, Koch said.

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In a statement, the United Nations Interim Security Force for Abyei (UNISFA) condemned the violence that killed the peacekeeper.

UNIFSA confirmed intercommunal clashes took place in the Nyinkuac, Majbong and Khadian areas leading to casualties and the evacuation of civilians to UNISFA bases.

“The UNISFA base in Agok came under attack by an armed group. The mission repelled the attack, but tragically a Ghanaian peacekeeper was killed,” the statement said.

Sudan and South Sudan have disagreed over control of the Abyei region since a 2005 peace deal ended decades of civil war between Sudan’s north and south. Both Sudan and South Sudan claim ownership of Abyei, whose status was unresolved after South Sudan became independent from Sudan in 2011.

The region’s majority Ngok Dinka people favor South Sudan, while the Misseriya nomads who come to Abyei to find pasture for their cattle favor Sudan. Currently, the region is under the control of South Sudan.

An African Union panel proposed a referendum for Abyei but there was disagreement over who could vote. Currently, the region is under the control of South Sudan.

Inter-communal and cross-border clashes have escalated since South Sudan deployed its troops to Abyei in March.