Syrian rebels pinned down in a strategic area where the Israeli and Lebanese borders meet with Syria were handed an ultimatum by the Syrian army and its Iranian-backed militia allies to either surrender or face certain military defeat, rebels said on Tuesday.

The Syrian army backed by local militias financed and equipped by Iran alongside Druze fighters from the area have been escalating a fierce assault against Sunni rebels in an enclave in the foothills of Mount Hermon, close to both the Israeli and Lebanese borders.

"They were given 72 hours to surrender with fighters to go to Idlib or those who want to stay have to reach a settlement," said Ibrahim al-Jebawi, a Free Syrian Army (FSA) official familiar with the situation on the ground.