A/HRC/18/40 their grievances over migration rights in the Abyei territory. The SPLM, on the other hand, holds the view that the Misseriya are only in Abyei for a short period of the year, and should not be allowed to vote in the referendum. 27. Tensions began rising when it became clear that the Abyei referendum would not be held as scheduled, and both the SAF and the SPLA increased their presence in the region in anticipation of future clashes. In the run-up to the South Sudan referendum, fighting erupted between Misseriya militias and the Abyei police in several locations in the region, which resulted in casualties on both sides and the displacement of a large number of civilians. Dialogue mediated by the United Nations resulted in the signing of two agreements, in Kadugli on 13 and 17 January. The agreement provided for the disarming of the feuding parties and allowed southerners returning from the North free movement through Abyei, while guaranteeing the Misseriya limited grazing rights through the Abyei corridor. The agreement also provided for the withdrawal of the Abyei police unit to be replaced by two new battalions of joint integrated units composed of SPLA and SAF troops. While the parties committed to demilitarization, extensive military build-up by both sides continued on the ground, leading to further clashes, including an attack on a SAF convoy on 1 May, which reportedly killed 11 SAF soldiers. 28. On 19 May, a United Nations convoy escorting SAF joint integrated units was ambushed by the SPLA in violation of the Kadugli agreement. Sudanese authorities reported that at least 22 of its soldiers were killed in the attack. On 21 May, the SAF retaliated by launching a full-scale aerial and ground offensive that culminated in the seizure and occupation of Abyei. The attack involved the use of heavy artillery, tanks and aircraft and the bombing of several villages in the area. Two UNMIS peacekeepers were injured when several shells fired by the SAF landed at the Mission compound. Most town residents managed to flee before the attack. An estimated 110,000 Abyei residents are believed to have fled southwards to various parts of South Sudan, including Agok and Turalei and other villages in Northern and Western Bahr el Ghazal, Unity and Warrap 11