President Vladimir Putin has ordered the Russian Navy's Northern Fleet and paratrooper units to go on full alert as part of snap military exercises in the Arctic, RIA news agency quoted the defence minister as saying on Monday.
Defence Minister Sergei Shoigu, who is overseeing an expensive modernisation of the armed forces, said Russia faced new threats to its security which obliged it to boost its military strength and capabilities.
"New challenges and threats to military security require the armed forces to further boost their military capabilities. Special attention must be paid to strategic formations in the North," state-run RIA quoted Shoigu as saying.
Tensions between Russia and the West have reached their worst level since the Cold War over the crisis in Ukraine.
The West and Kiev accuse Russia of supplying arms and soldiers to support pro-Russian separatists in eastern Ukraine who are fighting government troops.
NATO made new allegations last week that Russia was arming the separatists in east Ukraine, where more than 6,000 people have been killed in nearly a year of fighting.
Moscow has boosted its ambitions in the resource-rich Arctic region, where it shares a border with NATO member Norway, and the military is looking to boost its capabilities in the region.
The tests were due to include nearly 40,000 servicemen, 41 warships and 15 submarines, RIA reported.