NATO Secretary General Jens Stoltenberg here on Friday labeled the year 2014 as a "black year" for European security.

He made the remarks during the launch of the NATO Annual Report, while stressing that NATO had been "able to respond to the changing environment."

Stoltenberg said violent extremism close to NATO's southern borders was fueling terrorism in Allied countries, and that Russia's actions had destabilized eastern Ukraine.

"This Annual Report demonstrates that we are adapting to deal with these changes, and to keep NATO strong," said Stoltenberg.

He added that the Readiness Action Plan, which was agreed at the Wales summit, was being turned into reality, and the plan "will be the biggest reinforcement of our collective defence since the end of the Cold War."

The Secretary General said NATO remained the strongest military Alliance in the world, but, in order to respond to the new environment, Allies needed to spend more and to spend better.

He noted that last year NATO stopped the cuts in defence spending, to aim to spend 2 percent of Gross Domestic Product on defense within a decade.

"We have seen some steps in the right direction, but there is a long way to go," he said.

"Today, the security of Afghanistan is fully in Afghan hands. While many challenges remain, we are determined to support Afghanistan to build on the gains that we have made with great effort and sacrifice," wrote the Secretary General in the introduction to the report.