Armoured vehicles backed by troops pointing guns at unarmed soldiers have stormed a Ukrainian air base in Crimea as Russia’s defiant march across the rebel peninsula rolled on despite sanctions and growing global isolation.

The show of Russia’s unbridled might came as the chill in East-West relations intensified with a charge by Germany – a nation whose friendship Russian President Vladimir Putin had nurtured – of a Kremlin attempt to “splinter” Europe along Cold War-era lines.

Europe’s most explosive security crisis in decades will now dominate a nuclear security summit that kicks off in The Hague on Monday.

Russia is facing the loss of its coveted seat among the G8 group of leading nations for its use of force in response to last month’s fall of a pro-Kremlin regime in Kiev.

Crimea’s rebel authorities estimate they – together with Russian forces – control at least half of Ukraine’s bases on the Black Sea peninsula and about a third of its functioning naval vessels.

The most tension-fraught episode on Saturday saw gunmen dressed in fatigues similar to those worn by crack Russian forces break into the Belbek air base near the main city of Simferopol after an armoured personnel carrier blasted through the main gate.

Two more armoured personnel carriers followed and militias stormed in firing automatic weapons into the air and pointing guns at Ukrainian soldiers.

An AFP reporter heard stun grenades on the territory of the base before the situation calmed and the gunmen lowered their weapons. Several of the base’s unarmed soldiers began singing the Ukrainian national anthem during the ensuing lull.

“It’s so disappointing,” one told AFP. “So disappointing, that I don’t have any other words to say.”

Canadian Prime Minister Stephen Harper brought his own message of support for “courageous” Ukrainians on a first visit by a G7 leader since Crimea staged a contentious March 16 independence vote that the international community almost unanimously proclaimed illegal.

Harper said Putin had “undermined international confidence” by violating a 1994 deal under which Ukraine gave up its Soviet-era nuclear weapons in return for sovereignty guarantees from Russia and several Western states.

“By breaching that guarantee, President Putin has provided a rationale for those elsewhere … to arm themselves to the teeth,” Harper said.

The US and Europe have thus far limited their retaliation against Putin to targeted travel and financial sanctions that concern officials but do not impact the broader Russian economy.

Moscow’s only response has been to bar nine US officials and lawmakers from entering the country.