Russia's Pacific Fleet divisions take position in Kamchatka.
Strategic bombers redeployed Eastern Military District in snap exercises called by Vladimir Putin.
Troops and government ministries checked 'for fulfilling tasks under wartime conditions'.
Moscow has confirmed moves to modernise its military presence on islands over which Japan claims sovereignty.
100,000 troops and 5,000 weapons involved in the exercises in the Eastern Military District.
Based near Anadyr, its role is to 'monitor combat readiness' of military units, survey terrain, and air patrols.
Defence Ministry move seen as bolstering Russia's eastward tilt.
'Spy plane' was monitoring Siberia under Open Skies treaty aimed at reducing tension after Cold War.
Plane schedules disrupted, residents warned to stay indoors, sailors had to use GPS to get back to land because of thick smoke fumes from raging forest fires.
Flights late on Thursday and on Friday suffered disruption due to smog caused by blazes in dry woodland made vulnerable by the current heat wave.