MOSCOW -- President Vladimir Putin said Tuesday that a recent Russian military exercise has marked the beginning of a series of such drills this year, a show of force that comes amid a bitter strain with the West over Ukraine.

Reflecting the tensions, U.S. and other NATO forces staged manoeuvres in the Baltics, and a convoy of U.S. troops has driven through eastern Europe in a bid to reassure the allies.

Last week's Russian manoeuvres that spread from the Arctic to the Black Sea involved 80,000 troops, about 100 navy ships and more than 220 aircraft.

Defence Minister Sergei Shoigu reported to Putin Tuesday that the manoeuvres were aimed at checking the readiness of the newly formed group of forces in the Arctic, as well as the military's capability to quickly field troops to several theatres of operations.

"I proceed from the assumption that this was just the start of efforts to train the armed forces," Putin said.

As part of the drills, the state-of-the art Iskander missiles were deployed to Russia's westernmost exclave of Kaliningrad bordering NATO members Poland and Lithuania, and long-range, nuclear-capable Tu-22M3 bombers were sent to Crimea, the Black Sea peninsula Russia annexed from Ukraine a year ago.

The move was intended to demonstrate Russia's readiness to raise the ante amid a bitter strain in relations with the West, but for now the Kremlin apparently has stopped short of making the deployment permanent.

Shoigu reported to Putin that all troops involved in the manoeuvres have returned to their home bases.

Asked specifically if the Iskander missiles also had returned to their location, Putin's spokesman Dmitry Peskov referred to Shoigu's statement in comments carried by Russian news agencies.

Even though the latest manoeuvres ended last week, the Russian military continued their training.

NATO said it scrambled Danish and Italian jets based in Lithuania early Tuesday to escort four Russian military jets flying with their transponders switched off in international airspace over the Baltic Sea. The alliance said the Russian planes were heading to Kaliningrad.