Earlier, newspaper reports claimed that a huge manhunt was underway for the 40-year-old south Armagh man, suspected of training Palestinian militants.
According to security forces in Isreal, he is now being interrogated to discover the extent of the network he had developed.
It's understood he entered Isreal on a British passport three weeks ago, posing as a tourist, and from there slipped across the green line that divides the country from the West Bank.
Both the Gardai and PSNI have confirmed that they have known the Real IRA activist for more than a decade.
