Russia was conducting huge and unexpected war games on Tuesday, coinciding with a Nato drill in the Arctic at a time of heightened tensions in the region.

The snap check launched on the orders of President Vladimir Putin involved up to 700 units of military hardware, 12,000 troops and up to 250 aircraft, the defence ministry said.

Russia has recently intensified snap checks of its military might, testing its capabilities from the Arctic to the Far East as relations with the West have plunged to a post-Cold War low over the Ukraine crisis.

The latest exercises, over Russia's central military district from the Volga River to Siberia, began Monday -- the same day that NATO planes joined Nordic air forces to launch a simulated UN peacekeeping mission in Sweden's sub-Arctic north.

That drill, involving nine countries, comes as Nordic countries report increased Russian airforce activity close to their borders, and follows a pledge by the five Nordic nations to engage in closer military cooperation.

The aim of the latest Russian exercises is to allow Russian forces to resist a simulated attack from the air.

The drill focuses on the challenges of operating from unfamiliar bases in the field and moving troops to new positions both on foot and using railways.

Nuclear bombers will practise firing cruise missiles at targets on the ground at the Pemboi firing range in the remote northern Komi region.

Air defence missile units are also being deployed to simulate defending firing ranges in the southern Astrakhan region on the Caspian Sea.

Deputy defence minister Anatoly Antonov said Russia's drills were due to run until May 28. They are part of preparations for even larger exercises called Centre 2015, due in September this year.

The Nordic exercises continue until June 4 and will be followed on June 5 by NATO's annual Baltops (Baltic Operations )manoeuvres with 4,500 troops from 17 countries.