The ex-rebels, who will have a choice between returning to civilian life or joining regional or federal security forces, were formally re-integrated during a ceremony in the eastern city of Jijiga, reported the state media outlet Ethiopia News Agency.

The fighters, who were based in Eritrea, returned to Ethiopia in November 2018, shortly after a peace agreement was signed between the ONLF and the Ethiopian government.

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.

The rebel group made international headlines on April 24, 2007 when it launched a deadly raid on a Chinese run oil field in the Somali regional state.

The attack left 65 Ethiopians and nine Chinese dead.

After the attack, Addis Ababa launched a large scale counterinsurgency campaign, with rights groups alleging widespread abuses including torture, rape and murder.

Since taking office in April, Prime Minister Abiy Ahmed has released imprisoned dissidents and prioritised reconciling with the country's various opposition groups.

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 2018, also helped turn Asmara from a chief sponsor of ONLF to one that is mediating between the two sides.