South Sudan invaded and briefly occupied the small border town of Heglig before being pushed back by the Sudanese army.

Small-scale clashes continued until an agreement on borders and natural resources was signed on 26 September, resolving most aspects of the conflict.

[25] The United Nations Interim Security Force for Abyei, consisting of Ethiopian troops were deployed under a UNSC resolution from 27 June 2011.

[34][35] On 31 March, Sudanese warplanes bombed the Southern forces positions on the border, although officials from the north said it was artillery, not aircraft involved in the attack.

[38] The SPLA claimed that Teshwin in South Sudan had been attacked by Sudanese forces on 9 April with battle going on into the next day[39] The town of Abiemnhom in Unity was reportedly attacked by two brigades from the Sudanese army, which South Sudan claimed was an attempt to seize its oil fields.

The militia later transformed into a private army and became infamous for committing numerous atrocities during the subsequent South Sudanese Civil War.

"[57] South Sudan's vice president Reik Machar said a Sudanese attempt to retake Heglig by force was halted 30 km north of the town.

The Sudanese air force, operating two Sukhoi Su-25 jets,[59] reportedly bombed Jau and Panakuach, as well as Heglig once again,[60] killing five civilians.

[62] Two MiG-29s from the Sudanese Air Force attempted to destroy a bridge in Bentiu but missed their target and ended up killing four civilians and a soldier and wounding five others.

Sudan's military spokesman Al-Sawarmi Khalid revealed that their immediate objective was to "destroy the South's war machine", rather than enter Heglig itself.

South Sudan disputed the north's version of events as propaganda, claiming that northern forces were still 30 kilometres (19 miles) from Heglig.

[69] Rabie Abdelaty, a spokesman for the Sudanese government, ruled out peace talks with the South, saying it would hurt national pride if Sudan did not take back Heglig by force.

The clash was reportedly sparked when a South Sudanese soldier was shot dead when collecting water near the road between Aweil and Meiram.

[73] On the 22 April, more fighting broke out along the whole border as Sudanese soldiers backed by tanks and artillery launched three waves of attacks 10 kilometres (6 mi) into South Sudan.

[77][78] On 27 September, Omar al-Bashir and Salva Kiir signed eight agreements in Addis Ababa, Ethiopia, which led the way to resume important oil exports and create a 10 km (6 mi) demilitarised zone along their border.

[citation needed] Ethiopian Prime Minister Hailemariam Desalegn also praised the outcome and hoped it would build momentum.

[81] In mid-March 2013, both countries began to withdraw their forces from the border area in a bid to creating a demilitarised buffer zone and resume South Sudanese oil production for export through Sudan.

[88] A summit between the leaders of the two countries had been planned to be held in Juba some time in April 2012, following up from the meeting of the political, military, and security committee of the African Union on 30 March in Addis Ababa, Ethiopia.

[50] During Friday prayers on 13 April in Sudan, some sermons in Khartoum condemned the South Sudanese capture of Heglig, while television broadcasts included jihadi and patriotic songs.

[19] Parliamentary Speaker James Wani Igga called on people to prepare for war: "Khartoum might be meaning a real war ... if you don't defend yourself, you will be finished, so you should go and mobilise the people on [the] ground to be ready"[49] Parliament later decided to raise military spending and bolster the army by cutting salaries of all deputies by 10% for three months.

[95] On 27 March, a spokesman for Ban Ki-moon, the Secretary-General of the United Nations, called for the two countries to end the conflict and "use to the fullest extent existing political and security mechanisms to peacefully address their differences".

[92] On 15 April 2012, according to IRIB World Service, an Iran Broadcasting channel, Iranian Foreign Ministry Spokesman Ramin Mehmanparast said that Iran fully monitors the developments in the region, and calls on South Sudan to immediately and unconditionally pull back its forces and return to its territory behind the designated borders.

[99] Israel allegedly airlifted military hardware to the South Sudanese armed forces "on a daily basis" during the conflict.

[101] On 6 May 2012, Africa Minister Henry Bellingham supported the African Union-led initiative, calling for both sides to restart negotiations and comply with the ceasefire.

"[102] On 22 September 2012, Vietnamese Foreign Ministry Spokesman Luong Thanh Nghi calls for "concerned parties to abide by the international law and signed agreements, to restrain themselves and keep tensions from escalating while working on resolving disagreements by peaceful negotiations,"[103] On 21 April 2012, Yemen condemned South Sudan's occupation of Heglig, called for both parties to give diplomatic efforts a chance, and argued both sides should "establish ties enhancing the mutual confidence and building on the bonds of common history and human relations between the two countries.