NATO Secretary General Jens Stoltenberg said Thursday there had been a "troubling escalation" in Russian military activity in Syria, after Moscow expanded its air campaign against positions of Takfiri group, ISIL, in Syria.

NATO Secretary General Jens Stoltenberg said Thursday there had been a "troubling escalation" in Russian military activity in Syria, after Moscow expanded its air campaign against positions of Takfiri group, ISIL, in Syria.

"In Syria, we have seen a troubling escalation of Russian military activities. We will assess the latest developments and their implications for the security of the alliance," Stoltenberg said as he went into a NATO defense ministers meeting dominated by the Syrian crisis.

"This is particularly relevant in view of the recent violations of NATO's airspace by Russian aircraft," he added.

Asked if NATO would consider extending their mission in light of the Russian missile attacks, Stoltenberg said: "NATO is able and ready to defend all of the allies, including Turkey."

He cited measures taken to boost NATO's readiness, driven initially by Russia's intervention in support of pro-Moscow Ukraine rebels, and the creation of a very rapid response force which should be operational from next year.

This "spearhead" force, of about 13,000 troops, could be deployed both to the east and to the south if need be, he said.

"We are facing many challenges from many different directions. Conflict, instability and insecurity," he said.

"We are implementing the biggest reinforcement of our collective defense since the end of the Cold War."

Moscow launched its military operation against ISIL terrorists at the request of the Syrian government on September 30. Since the start of the operation, the Russian military have destroyed at least 112 objects belonging to Takfiris.

Among them are 19 commanding points, 12 ammunition depots, 71 armored vehicles and six factories that produced explosive devices, Russian Defense Minister Sergey Shoigu said Wednesday.