The African Union (AU) called on Thursday for an urgent meeting of the leaders from Sudan and South Sudan to find a solution for the flashpoint Abyei region after the killing of a tribal leader and an Ethiopian peacekeeper.

On Saturday, Kuwal Deng Mayok, the chief of the Dinka tribe allied to South Sudan, was killed by a member of the Misseriya tribe in Abyei claimed by Khartoum and Juba. One Ethiopian peacekeeper and 15 Misseriya, who are allied to Sudan, also died, according to the United Nations and the Misseriya.

In March, the African Union brokered a deal between Sudan and South Sudan to resume cross-border oil flows and defuse tensions which have plagued them since the South seceded in 2011 after an independence vote.

READ: Sudans move closer to peace

But despite several recent meetings, Sudan's President Omar Hassan al-Bashir and South Sudan's Salva Kiir have been unable to agree on the ownership of Abyei, which the Dinka and the Arab Misseriya call their home.

Making a new push, the AU "urges the two Heads of State... to meet immediately", according to a statement released in Addis Ababa. "This grave incident that occurred in Abyei serves to underscore that the status quo in Abyei is not tenable."

Abyei straddles the border between the two Sudans, which fought one of Africa's longest civil wars. The province is prized for its fertile land and small oil reserves.

READ: Abyei, major obstacle to ceasefire

Like South Sudan, Abyei was meant to have an independence vote, agreed under the 2005 peace deal which ended the civil war between the north and south. But Sudan and South Sudan have been unable to agree which tribal members should participate.

Ethiopian peacekeepers have been administering Abyei since Sudan seized it in May 2011 following an attack on a convoy of UN peacekeepers and Sudanese soldiers which the United Nations blamed on southern forces. Khartoum later withdrew its forces under a UN peace plan.