Anti-terror detectives in Likoni raided a house where he was hiding in Mrima and recovered a G3 rifle.
However, three others suspects hiding with him managed to escape the police dragnet.
Police Chief Willy Simba speaking at Likoni police station said that Ali upon interrogation admitted he was trained in Somalia and returned to Kenya earlier this year.
Simba said they are questioning him about other returnees for more leads.
According to Simba, Likoni has been a hideout for most-wanted criminals from Kwale and Mombasa. Likoni said to be a training ground for MRC recruits.
Ali’s arrest was made following tip off from local residents.