Belfast man Mr Seán Ó Muireagáin will hold a press conference in Belfast later today after flying out of Israel last night.
He stayed in London last night after Israeli authorities released him from custody. Mr Ó Muireagáin was questioned about alleged republican activities, but his family and friends say he was a victim of mistaken identity.
He was released after a senior official in the Israeli government said the Shin Bet security service was satisfied he did not pose a danger to Israeli citizens.
"It's not a concern we have," said the official. "We have real terrorists that we have to deal with and we are satisfied that that is not what we were dealing with in this case".
Mr Ó Muireagáin was arrested on Saturday, July 12th, and is known to have been questioned about alleged links between dissident republicans and Palestinian militants.
He had been sending articles from Israel for the Irish language newspaper Láwhen taken into custody last Saturday near Ramallah.
He was described by friends as an Irish language activist and a member of a Palestinian solidarity group. He had travelled to Israel to set up a joint Irish-Palestinian educational project to twin schools in the West Bank with schools in the North.