NATO flexed its muscles Thursday in Poland during the first full drill of its new spearhead force, a structure designed to boost security on its eastern flank in the wake of Russia's annexation of Crimea from Ukraine.

Around 2,100 soldiers from nine NATO states grouped in the Very High Readiness Joint Task Force (VJTF) took part in the Noble Jump 2 exercises at the Zagan training range north-western Poland.

The drill comes as the conflict in Ukraine has pushed Russia and the West into their worst standoff since the collapse of the Soviet Union.

The vast training range is stoked with adrenaline -- an armed man guarding a mock militia headquarters drops to the ground after being 'shot' by special forces.

A militia commander code-named Birdman tries but fails to escape the scene in a jeep as soldiers armed to the teeth tackle him by swooping down from helicopters hovering overhead.

In scenes strongly reminiscent of fighting in eastern Ukraine between separatist insurgents and government forces, special forces overcome other militiamen as F-16 fighter jets buzz insurgents armed with heavy weapons and allied to the militia.

US, Belgian, Czech, Dutch, German, Hungarian, Lithuanian, Norwegian and Polish troops have been preparing since last week for this full-scale exercise.

NATO allies decided last year to create the VJTF in response to Russia's annexation of Crimea.

The alliance has also mounted a series of military drills on its eastern flank to counter Russia's increased military presence in the Baltic Sea and regional airspace, an area which lay behind the Iron Curtain 25 years ago.

"If NATO is ready today it's because we trained yesterday. It is not a coincidence," General Jean-Paul Palomeros, NATO's Supreme Allied Commander for Transformation.

- 'Post-Cold War peace over' -

Visiting the troops on Wedneday, NATO Secretary General Jens Stoltenberg said the alliance was "implementing the biggest reinforcement of our collective defences since the end of the Cold War", after Russia announced that it would boost its nuclear arsenal this year.

Moscow was responding to reported US plans to deploy heavy weapons to its jittery NATO allies in eastern Europe, with Putin saying the US-led alliance is "coming to our borders".

NATO member Poland went so far as to insist Thursday that the post-Cold War period of peace is "now over", as the European Union grapples with various crises including the Ukraine conflict and terrorism.

"After tens of years of peace, that peaceful period after the Cold War is now over," Defence Minister Tomasz Siemoniak told reporters in Zagan.

"Because there are more and more crises erupting around Europe... It's not only the Ukrainian and Russian crisis but also ISIS and a number of different crises in northern Africa," he said, using an acronym to refer to the jihadist Islamic State group.

Stoltenberg also said Thursday the Alliance would address the question of whether to store military equipment on eastern members' soil next week at a NATO defence ministerial meeting in Brussels.

"I foresee decisions later on regarding the question of prepositioning of equipment in the eastern part of the alliance," he said.

Siemoniak meanwhile said that Poland was waiting on a decision from the US on the heavy weaponry, adding that he expected it to be made in the next few weeks and hoped it would be "positive".

Under Moscow's thumb in Soviet times, the three Baltics states last month asked NATO to deploy several thousand permanent troops in their region as a deterrent to Russia but so far there has been no response from the alliance.

But some European NATO allies, like Germany, have been sceptical about a substantial permanent deployment, saying it could breach a 1997 agreement between NATO and Russia.