Russia, in a little-noticed move, has carried out a barrage of missile tests across its Arctic territories in what’s described as one of the most massive nuclear missile drills in post-Soviet history.

The Independent Barents Observer reports that Russia’s military fired four ballistic missiles, two in each direction, across the Arctic hemisphere on Thursday evening. The exercises are the latest in what Scandinavian analysts say is a noticeable rise in Russian military activity in a region whose economic importance is growing due to global warming.

The Norway-based news website says two missiles were launched from a Pacific Fleet submarine in the Sea of Okhotsk towards the Chizha test range on the Kanin Peninsula in Arkhangelsk. A Northern Fleet submarine, in another test, is said to have launched another ballistic missile from the Barents Sea. This missile reportedly hit a target in the Kura test range on the Kamchatka Peninsula in the Far East.

A Topol ballistic missile was also launched the same day from Plesetsk in Russia’s Arkhangelsk region, reportedly streaking across the Arctic before its dummy warhead hit a target at the Kura test range in northern Kamchatka Krai in the Russian Far East

Long-range Russian Tu-160 and Tu-95 strategic bombers, as well as Tu-22M bombers are also said to have tested cruise missiles in Kamchatka in the Far East and in Kazakhstan in Central Asia.

Russia’s Defense Ministry acknowledged the tests and said that all were completed successfully.

Russia has accelerated a military buildup in its Arctic region over the last several years. The activity includes the construction of new Arctic bases and the deployment of specialized Arctic military units and equipment, including helicopters, icebreakers and armored vehicles. Moscow is also reportedly developing a new class of nuclear-powered destroyers that can protect its Northern Sea Route.