Israel's military is considering the possibility of working with Lebanon's army to fight against extremist militants, despite the fact the two countries are officially at war.

A senior Israeli military officer pointed to the broad coalition of countries that have joined together to fight Islamic State (Isis) in Iraq and Syria and said Israel could try to expand its range of security allies in the region.

"If you all have a common enemy, it should be very easy to find common opportunities to try to fight it," said the officer, who spoke on condition of anonymity, as cited by Reuters news agency.

"And I am looking and asking myself: Will the Lebanese Armed Forces play a positive or negative role?"

This could involve mediated cooperation with Lebanon's army, he added, but did not state whether any contact had been made.

The idea of public coordination with Israel is likely to be rebuffed in Lebanon, where working with Israel is deemed to be a crime.

While Lebanon has been engaged in fighting against extremist militants around its border with Syria, the fractured nature of the conflict makes the possibility of cooperation appear far-fetched.

Militants from Shia-aligned Lebanese group Hezbollah have been fighting in support of the Syrian government inside the country for more than 18 months.

Meanwhile, Israel is thought to have carried out a series of air strikes against Syrian government positions over the course of the war, in a bid to stop military equipment falling in to Hezbollah's possession.