The Russian president said he would use nuclear only as security protection.

Speaking on a documentary broadcast on Russian TV, Putin said he would not wield the "nuclear big stick".

But he threatened to liquidate ISIS terrorists with nuclear warheads if conventional bombing raids fail to destroy the terror group.

The Russian president warned that his military's cruise missiles could be fitted with atomic weapons.

During a televised meeting with defence minister Sergey Shoigu, Putin said: "We must analyse everything happening on the battlefield, how the weapons operate.

"The Kalibrs [cruise missiles fired from the sea] and KH-101 [cruise missile fired from jets] have proved to be modern and highly effective, and now we know it for sure - precision weapons that can be equipped with both conventional and special warheads, which are nuclear."

But he added that launching a nuclear strike on ISIS in their Iraqi and Syrian heartlands would only be used as a last resort.

He said: "Naturally, this is not necessary when fighting terrorists and, I hope, will never be needed", Express reported.

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