Four IDF soldiers sustained light and moderate injuries when an explosive device went off near the Lebanese border overnight Wednesday.The soldiers were airlifted to the Nahariya Hospital for the Western Galilee for treatment.Herb Keinon and Reuters contributed to this report.For most of Wednesday, security officials declined to comment on the incident, until Defense Minister Moshe Ya'alon broke the official silence to say that the soldiers were on a routine mission to ensure quiet along the border "for northern residents" and "the residents of Israel in general.""During the operational activity, the force went over an explosive device. We are of course investigating the incident, [and seeking to verify] if this is an old or new device," the defense minister added.The IDF said it was monitoring developments on the northern border.Prime Minister Binyamin Netanyahu briefly referred to the incident, saying Israel would “continue to act responsibly in order to defend Israel’s borders."Commenting on the incident, the Lebanese Army said that in a "violation of Lebanese sovereignty", an Israeli infantry patrol crossed the UN-designated "blue line" between the two countries and moved 400 meters inside Lebanese territory."During the infiltration, an explosion occurred which led to a number of them being wounded," the Lebanese military said, adding it was investigating the circumstances of the blast in coordination with UN peacekeepers in southern Lebanon.Earlier, a Lebanese security source said the incident may have taken place north of the border fence which separates Israeli and Lebanese forces, but on the Israeli side of the line.He said the soldiers may have been wounded by a mine.Another Lebanese security source said the explosion was 150 meters south of the blue line.Hezbollah's Al-Manar television channel claimed that the soldiers had been engaged on a classified security mission.Meanwhile on Wednesday, Lebanese media outlets said an unexplained explosion tore through a tunnel network controlled by the Popular Front for the Liberation of Palestinian – General Command, at one of the terrorist organization's main bases of operation in the Lebanese town of Naameh, south of Beirut.Quoting Lebanon's National News Agency, the Ya Libnan website said "intense gunfire" could be heard after Tuesday night's blast.There were no additional details available.