Ukraine crisis: Pro-Russian troops storm naval base as Clinton warns of 'aggression' from Putin

Pro-Russian forces have been seen taking a navy base in Sevestapol hours after Russia signed a treaty on Crimea

Pro-Russian protesters hold a Russian, Crimean and Soviet flags during their rally at Lenin Square in Simferopol, Ukraine (EPA)

Pro-Russian troops stormed a Ukraine navy base this morning as Hillary Clinton warned other countries near Russia face aggression if President Vladimir Putin is “allowed to get away with” his actions, hours after he signed a treaty on the annexation of Crimea.

Clinton warned that a "two-track" approach toward resolving the crisis that included economic incentives and "standing up for our values” would be taken, shortly after President Putin claimed Crimea for his country in a 66-minute speech laced with invectives against the West and a robust reassertion of Russian power.

"If he's allowed to get away with that, I think you'll see a lot of other countries either directly facing Russian aggression or suborned with their political systems so that they are so intimidated that in effect they are transformed into vassals, not sovereign democracies," Clinton said at an event hosted by the Board of Trade of Metropolitan Montreal at the Palais des Congres.

Meanwhile, the Russian flag was seen flying over the Ukrainian navy's headquarters in the Black Sea port of Sevastopol.

Men in plain clothes were seen entering a building at the naval headquarters.

Ukrainian navy spokesman Sergiy Bogdanov said: "There are about 200 of them, some wearing balaclavas. They are unarmed and no shots have been fired from our side. The officers have barricaded themselves inside the building.”

Tensions increased in Crimea yesterday as Ukraine’s military said an officer had been killed in a confrontation at base in the capital Simferopol, hours after Russian and Crimean leaders signed a treaty absorbing the region into the Russian Federation.

The treaty says Crimea is considered part of Russia from the day of its signing but that it enters into force when it is ratified. Russia also plans to adopt legislation making Crimea one of its constituent regions.

The treaty states that: "in the hearts and minds of people, Crimea has always been and remains an inseparable part of Russia."

At the same time, pro-Russian authorities reported that a member of their own forces had also been killed in the incident.

On Tuesday, the Russian Foreign Minister Sergei Lavrov condemned Western sanctions over the Crimea dispute as "unacceptable" and threatened consequences during a phone call with the US Secretary of State John Kerry.

Russia accused Western states of violating a pledge to respect Ukraine's sovereignty and political independence under a 1994 security assurance agreement, saying they had "indulged a coup d'etat" that ousted President Viktor Yanukovich last month.

The Foreign Ministry said actions by the US and EU ran counter to assurances granted by the United States, Britain and Russia in exchange for Ukraine's commitment to give up its nuclear arsenal after the Soviet collapse.

Mr Putin said he did want to "carve up" Ukraine but warned the West it had "crossed a line" over Crimea.

The United States and the European Union on imposed sanctions on Russia earlier this week, targeting Russian and Crimean officials with visa bans and asset freezes.

Additional reporting by agencies