Israel's military chief Benny Gantz said on Monday that "terrorist" groups fighting the regime of Syrian President Bashar al-Assad alongside other insurgents were becoming stronger.
"The situation in Syria has become exceptionally dangerous. The terrorist organisations are becoming stronger on the ground. Now they are fighting against Assad but in the future they could turn against us," Gantz said.
The Israeli chief of staff, who was addressing an annual security conference, warned that the Syrian army's "very important" arsenal "could fall into the hands of these terrorist organisations."
Several radical Islamist groups have joined the ranks of the nearly two-year Syrian rebellion against Assad's regime, Al-Nusra Front being the most prominent.
Completely unknown before the uprising began, it has been a rebel standard-bearer since mid-2012 when it became the spearhead of the insurgency ahead of the Free Syrian Army.
FSA fighters, composed mainly of army deserters, have told AFP that despite being fewer in number, the Al-Nusra jihadists have better logistic and economic backing and receive financing "from abroad."