Russia and Nato have launched rival military exercises in the latest sign of rising military tensions in eastern and central Europe.
About 250 aircraft and 12,000 servicemen will take part in Russian combat readiness drills over the Urals mountains and Siberia in what the country's defence ministry has described as a "massive surprise inspection".
The snap exercises launched yesterday in Russia's central military district began on the same day Nato launched its own long-planned exercises in the Arctic.
About 100 aircraft and 4,000 servicemen will take part in "Arctic Challenge", a Norwegian-led aviation exercise described as the "largest of its kind".
The two-week exercise will involve forces from Germany, Britain, France, the Netherlands and the United States, as well as non-Nato allies Finland, Sweden and Switzerland.
Tensions between Russia and the North Atlantic alliance have been heightened over the conflict in Ukraine.
Russian exercises in its Western and Central military districts have been denounced as "sabrerattling" in the West, which accuses Russia of effectively invading Ukraine by stealth.
And Moscow has hit out at a series of Nato land, air, and sea exercises that the alliance says are designed to reassure eastern alliance members and non-Nato allies.
Dmitry Rogozin, the deputy prime minister with responsibility for defence, further raised tensions over the weekend when he joked on national television that "tanks don't need visas".
The comment came in response to a question about US and EU sanctions and visa bans imposed on several prominent Russian politicians and businessmen.
Mr Rogozin - a former leader of the far-right Rodina party - tweeted on Sunday that Russia poses no threat to the West - which he added was facing "collapse under the onslaught of ISIS (Isil) and gays". (© Daily Telegraph, London)