(Adds Lebanese Army comment)
JERUSALEM, Aug 7 (Reuters) - An explosion at the border with Lebanon wounded four Israeli soldiers on Wednesday, and the Lebanese Army said the troops were inside Lebanese territory when the blast occurred.
The soldiers were involved in "an activity near the border", an Israeli military spokesman said about the nighttime incident, without providing details about their exact location or what caused the explosion.
Four soldiers were wounded and taken to hospital in Israel, the spokesman said.
Israeli forces routinely patrol the frontier with Lebanon, which has been largely quiet since a war with Lebanese Hezbollah guerrillas in 2006.
The Lebanese Army said that in a "violation of Lebanese sovereignty", an Israeli infantry patrol crossed the U.N.-designated "blue line" between the two countries and moved 400 metres (yards) 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 U.N. 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 security source said the explosion was 150 metres (yards) south of the blue line.
Asked about the incident, Andrea Teneti, a spokesman for the peacekeeping force, UNIFIL, said he had "no information in relation to our mandate of operations", and he described the situation as calm. (Reporting by Allyn Fisher-Ilan in Jerusalem and Oliver Holmes in Beirut, Editing by Jeffrey Heller and Elizabeth Piper)