Moderate rebel groups on the border have collapsed, and their men have joined Isil

Islamic State of Iraq and the Levant fighters in Syria, massed close to the Lebanese border, are threatening to launch attacks across it, the Telegraph has witnessed.

The group has been training new recruits and defectors from smaller rebel factions in Qalamoun, a militarily strategically important province in the south-west of Syria that borders Lebanon.

Several of those smaller rebel groupings, some aligned with the more moderate "Free Syrian Army", have capitulated to the jihadists in recent months with many of their fighters joining Isil.

The growth of the group in the area means Sunni Isil fighters in Syria are now at the edge of the Lebanese heartland of its Shia arch enemy Hizbollah, whose men are fighting alongside the regime of Bashar al-Assad.

Islamic State fighters mass on Lebanon border and threaten to launch attacks across it