Lebanon and Israel are in a state of war and each bans its citizens from visiting the other country. There are no border crossings at the tightly-controlled frontier. The military official, who spoke Thursday on condition of anonymity in line with regulations, gave no further details saying the man is being questioned and once they have information the army will release a statement.
State-run National News Agency said the man who was detained is a U.S. citizen adding that he was detained in the southern port-city of Tyre where he had been staying since Tuesday. It added that the man is being questioned under the supervision of judicial authorities.
The U.S. Embassy said in a statement: "We've seen media reports of the arrest of a U.S. citizen. We take our obligation to assist U.S. citizens abroad seriously and stand ready to provide all appropriate consular services."
It added that due to privacy considerations, "we have no further comment." Suspicion about someone crossing the tightly guarded border known as the Blue Line began to surface on Tuesday. The Israeli military said: "Israeli army troops identified a break in the fence and signs that point to the suspicion of a person crossing the border from Israel into Lebanon. The incident is under investigation."
Associated Press writer Ilan Ben Zion contributed to this report from Jerusalem.