Here is a timeline of developments in Sudan's disputed, oil-producing Abyei region which was seized by the northern army over the weekend, bringing the country's north and south to the brink of full conflict.
2005 - Sudan's government signs a peace deal with southern Sudan People's Liberation Movement (SPLM) rebels, ending decades of civil war.
-- Abyei, a fertile, oil-producing area on Sudan's ill-defined north-south border, claimed by both sides, was a key battleground during that conflict.
The peace deal does not settle the ownership of the area or set its borders but promises Abyei residents a referendum over whether they want to join the north or south. It also promises southerners a separate referendum on whether to secede from the north.
May 2008 - Clashes in the Abyei region -- close to oil fields claimed by both the north and the south -- kill at least 90, drive 50,000 from their homes and burn down Abyei town.
June 21 - The former north-south foes agree that an international court should decide on Abyei's boundaries.
July 22, 2009 - The Permanent Court of Arbitration in The Hague adjusts boundaries drawn up by an earlier panel, pulling in Abyei's borders to the north, east and west. Northern and southern leaders promise to respect the ruling.
-- Maps of the new boundary published in The Hague leave the area's key Heglig and Bamboo oilfields outside Abyei, placing them in the north Sudan district of Southern Kordofan while leaving huge tracts of fertile land inside Abyei.
-- Arab Misseriya nomads, linked to the north, protest against the border change saying it robs them of pasture land. Members of the south-linked Dinka Ngok tribe, that live in Abyei, welcome the ruling.
July 27 - North and south Sudanese leaders trade accusations over control of oilfields and details of the Abyei referendum just five days after agreeing the ruling.
December 29 - Sudan's government passes a law authorizing the referendum on southern independence. The next day the Abyei referendum law is also passed.
August 1, 2010 - Talks stall between Sudan's rival northern and southern halves over Abyei. The sides cannot agree on the makeup of a commission to organize the vote, and on who will be able to vote.
October 12 - The latest round of north-south talks on Abyei fail. Two days later north Sudanese leaders say it is impossible to hold the referendum on time and that the poll will have to be delayed or settled without a vote.
-- An official from the south says a delay is "unacceptable."
January 9, 2011 - Millions of jubilant south Sudanese vote to split from the north in their secession referendum. The separation is due to take place on July 9, 2011. The Abyei referendum does not take place.
-- The independence referendum is marred by clashes between north and south-linked groups in border areas, including Abyei.
March 4 - Thousands of people have fled Abyei, leaving large parts of it empty, aid workers say, after a surge in fighting leaves dozens dead. The U.N. says it is moving more than 100 new peacekeepers into the area to help quell violence.
March 30 - Sudan's north and south have deployed forces with heavy weapons to Abyei, the U.N. says.
April 28 - Bashir says he will not recognize South Sudan as an independent state if it claims the oil-producing Abyei region. The south's draft constitution, seen by Reuters, includes a claim to Abyei.
May 20 - South Sudan's army accuses the north of using tanks and artillery in attacks on four villages. North Sudan's army accuses the south of ambushing northern troops traveling in a convoy with U.N. peacekeepers.
May 21/22 - Khartoum sends tanks into Abyei town, the area's main settlement, forcing thousands to flee. The north says it is clearing out southern troops that have moved into the area, breaking earlier agreements. The move is condemned by U.N. Security Council envoys, Britain and Washington.