Ethiopia said on Monday it had signed a peace deal with the separatist Ogaden National Liberation Front (ONLF), formally ending more than three decades of insurgency in the eastern Somali regional state.Formed in 1984, ONLF had been fighting for the rights of ethnic Somalis living in eastern Ethiopia to self-determination, including the option of secession.Ethiopia's Foreign Minister Workneh Gebeyehu and the vice-president of the Somali regional state Mustafa Omer travelled to the Eritrean capital Asmara to hammer out the peace deal with the ONLF."The Ethiopian government and ONLF delegations held productive discussions and reached a historic deal that allows the ONLF to undertake a peaceful political struggle in Ethiopia," the foreign ministry said.Since taking office in April, Prime Minister Abiy Ahmed has released imprisoned dissidents and prioritised reconciling with the country's various opposition groups.The peace talks took place after the Ethiopian parliament in July removed the ONLF from a terror list, which prompted the group to declare an indefinite unilateral ceasefire in August.Ethiopia's breakneck diplomatic thaw with former rival Eritrea since July, also helped turn Asmara from a chief sponsor of ONLF to one that is mediating between the two sides. The ONLF made international headlines on April 24, 2007, when it launched a deadly raid on a Chinese run oil field in Somali regional state. The attack left 65 Ethiopians and nine Chinese dead.After the attack, the Ethiopian government undertook a large scale counterinsurgency campaign, with rights groups accusing Addis Ababa of widespread abuses including torture, rape and murder.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.