JERUSALEM (AFP) - Israeli and Lebanese troops exchanged fire on their often tense border on Monday morning, officials on both sides said, with the two armies trading accusations on why the shooting happened. The Israeli military said its troops had been fired on as they worked on the Israeli side of the Blue Line, the UN-drawn border with Lebanon. But a Lebanese army official said troops opened fire only when Israeli soldiers crossed the border line, which was established in 2000. Both sides have challenged the accuracy of the Blue Line in several locations."Earlier this morning an IDF (Israeli military) force carrying out a routine patrol within Israeli territory near the Israel-Lebanon border was fired upon from the direction of Lebanon," an Israeli military spokeswoman told AFP. "The force responded by firing towards the source of fire and UNIFIL was informed of the incident," she added, referring to the UN peacekeeping force stationed on the Israeli-Lebanese border. One Israeli military source said the incident occurred near the Dan kibbutz in the far north of Israel as troops carried out work on a border fence.