NATO chief Jens Stoltenberg on Wednesday said the alliance is looking to step up efforts to strengthen its eastern flank, warning that the threat from Russia had become the "new normal in Europe."

"Moscow has made it clear that it is prepared to contest the fundamental principles that have underpinned our security for decades and to do so by using force. I regret to say that this is the new normal in Europe," Stoltenberg said after a meeting of NATO defence ministers.

"Today, ministers decided to develop options to further strengthen NATO's deterrence and defence, including to consider establishing new NATO battle groups in central and southeastern Europe," he added.

The NATO chief said NATO military commanders will work on details and report back within weeks.

The comments come on the back of Russia's move to amass forces near the Ukrainian border, which heightened tension within the alliance.

Earlier, Moscow said it was pulling back the troops from near the frontiers, but U.S. Secretary of State Antony Blinken said U.S. is yet to see any evidence of a significant withdrawal.

(With input from agencies)