All roads leading to the predominantly Sunni town of Qara Tappah, about 120km (75 miles) north-east of Baghdad, were blocked by armed tribesmen, AP news agency reported.

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Members of the Sudanese Armed Forces removed the "armed tribesmen" from Kutum town last Saturday, but the militiamen returned a day later to fight again, the OCHA said.

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The challenge of "securing a cease-fire, removing armed tribesmen from urban centers, returning the military to the barracks and engaging in military-security reform will be serious stumbling blocks post-signing, " according to Longley Alley.

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Musa Hilal has armed many of his tribesmen.

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