BRUSSELS (AFP) - NATO head Anders Fogh Rasmussen on Thursday warned Russia not take any action over Crimea that could stoke tensions or misunderstandings in the Ukraine crisis.

"I'm concerned about developments in Crimea," Rasmussen said in a tweeted message.

"I urge Russia not to take any action that can escalate tension or create misunderstanding," he said.

Rasmussen's comments were made as the Ukraine interim government called in Moscow's representative in Kiev to warn that Russia must respect its territorial integrity after pro-Russian gunmen seized control of government buildings in the Crimea peninsula.

Russia must uphold the "independence, sovereignty and existing borders of Ukraine," the foreign ministry said.

Rasmussen later told a meeting of the NATO-Ukraine Commission that the latest developments in Crimea were "dangerous and irresponsible."

"I urge all parties to step back from confrontation," he said, calling on the Kiev authorities to lead the country forward in the most inclusive political process possible.

NATO defense ministers on Wednesday agreed a statement which said a sovereign, independent and stable Ukraine was essential to security in Europe.

"NATO allies will continue to support Ukrainian sovereignty and independence, territorial integrity, democratic development, and the principle of inviolability of frontiers, as key factors of stability and security in Central and Eastern Europe and on the continent as a whole," the statement said.

Rasmussen said after the statement that "Ukraine is the most important security issue in Europe today."

The latest developments have stoked growing concern about Ukraine's future and the possible wider fallout after the ouster of pro-Russian president Viktor Yanukovych.

Crimea is especially sensitive as the home base for Russia's Black Sea fleet and tensions there took on an added dimension after President Vladimir Putin ordered military preparedness checks in western Russia on Wednesday.

The interim Ukraine government specifically warned the Russian navy Thursday to keep its troops in their bases.

"Any troop movements will be considered as military aggression," acting president Oleksandr Turchynov told parliament.

In 1997, NATO set up a joint commission with Ukraine to oversee relations and in 2008 agreed that Kiev could eventually be considered for membership of the Cold War-era alliance.

The NATO-Ukraine Commission meeting was put on the agenda of the NATO defence ministers gathering at the last moment as the crisis worsened.