A 2005 peace agreement ended more than two decades of civil war fought between African rebels in the south of Sudan, and the government in Khartoum in the mostly Muslim, Arabic-speaking north.
But despite the accord, north-south tensions have persisted after South Sudan's independence in 2011, the first anniversary of which is being celebrated in Juba on Monday.
Here is a look at events since the 2005 peace accord:
January 9, 2005 - Southern rebel leader John Garang and chief government negotiator Vice President Ali Osman Mohamed Taha sign a comprehensive peace agreement ending the civil war. The agreement shares oil revenues between the north and south, sets up a coalition government and promises elections. The south is granted a 2011 referendum on possible secession.
July 9, 2005 - Garang is sworn in as first vice-president of Sudan. Three weeks later he is killed in a helicopter crash. Days of riots follow, killing 100 people.
August 11, 2005 - Salva Kiir, the last surviving founding member of the south's dominant Sudan People's Liberation Movement (SPLM), is sworn in as first vice president. Sudan's new power-sharing government is announced in Khartoum in September.
December 29, 2009 - Sudan's NCP and the SPLM pass the referendum law outlining the terms of the planned vote on southern independence, ending months of wrangling.
January 9, 2011 - Millions of jubilant southern Sudanese vote to split from the north in their secession referendum. A separate promised referendum on whether the disputed Abyei region should also join the south does not take place.
May 31, 2011 - Representatives from north and south Sudan agree to set up a Common Border Zone between north and south Sudan, which is to be demilitarized and monitored and patrolled, the African Union says.
July 9, 2011 - Kiir, standing next to his old foe, Sudan's President Omar Hassan al-Bashir, is sworn in as president of South Sudan, formally declaring independence from Sudan.
January 23, 2012 - South Sudan starts shutting down oil production and accuses Sudan of seizing $815 million worth of crude, escalating an increasingly bitter row over oil revenues.
February 10, 2012 - Sudan and South Sudan sign a security agreement which aims to defuse tensions over oil payments. Both countries have failed to agree on how much the landlocked South should pay to transport its oil through Sudan.
March 26, 2012 - Bashir suspends plans to fly to South Sudan to meet Kiir, after the South's forces occupy the oil-producing area of Heglig, parts of which are claimed by both countries.
April 19, 2012 - Bashir threatens war against South Sudan, vowing to teach his new neighbor a "final lesson by force" after it seizes Heglig. Two days later South Sudan withdraws and accuses its neighbor of bombing its troops as they pull out.
April 23, 2012 - Sudan carries out air strikes on South Sudan killing three people near the oil town of Bentiu, witnesses and the South's army say. Sudan denies the attack.
May 2, 2012 - The U.N. Security Council endorses an African Union roadmap demanding Khartoum and Juba conclude a deal over outstanding issues before August, or they could face sanctions.
June 21, 2012 - Sudan's armed forces clash with rebels in the oil-producing border state of South Kordofan, the two sides say, both claiming victory over the other.
July 1, 2012 - Sudan announces that Kiir and Bashir plan to meet on the sidelines of an African Union summit in mid-July.
(Reporting by David Cutler, London Editorial Reference Unit; Editing by Pascal Fletcher)