Robow Ali Abu Mansoor, the former Al-Shabaab deputy leader, has renounced ties with the Al-Qaeda linked militant group he helped form.
At a press conference in Mogadishu on Tuesday, Mr Mansoor said he abandoned the Somali jihadist group more than five years ago.
“I am going to make it clear for the Somali people and the world that I had withdrawn my membership in Al-Shabaab five years and seven months ago,” he said.
Mr Mansoor fell out with militant leaders in 2013 and remained a fugitive in southwestern Somalia.
He surrendered to the Somali government on Sunday at Hudur town, 420km southwest of capital Mogadishu.
He said he is holding talks with the government, adding that he hopes they would bear positive results and “lead to lasting peace in the country”.
In June, the United States dropped Mr Mansoor from its terror list and lifted a $5 million bounty for information leading to his arrest.
He had been placed on the list in 2008 and the bounty placed in 2012.