Putin visits Crimea amid military buildup on Ukraine border

Tensions between Russia and Ukraine are heating up even more as President Vladimir Putin landed in Crimea on Friday to meet with his security council just after Moscow announced it's putting advanced anti-aircraft missiles there.

Over the last week, the number of heavy weapons deployed near the front lines in eastern Ukraine has doubled, part of a pattern of Russia ramping up its military presence in the region throughout the summer. An estimated 40,000 soldiers have been stationed there, on top of aircraft and the anti-missile defense system.

All of this has been stoking fears Russia could be planning another invasion, two years after it formally annexed Crimea, as peace talks crumble. It's Putin's first visit to the territory since March.

Last week, Moscow accused Ukrainian officials of resorting to "the practice of terror" by sending sabotage teams armed with explosives into Crimea, and alleged that Ukraine was responsible for the deaths of two Russian soldiers.

"This is a very dangerous game," Putin warned on state television. "We obviously will not let such things slide by."

Ukrainian President Petro Poroshenko described the accusations as "preposterous," and only excuses for Russia to start a new border war.

"These fantasies are only a pretext for making more military threats against Ukraine," added Poroshenko, who has put his military on high alert over concerns that Moscow could launch a "full-scale invasion alone all fronts."

US officials and observers are not entirely convinced that Putin is planning a new offensive, saying the latest moves might be part of routine troop rotations, or efforts to instill patriotism ahead of the parliamentary elections in September.

"It's highly unlikely that the Russians are truly planning some major offensive," Mark Galeotti, an expert on Russia at New York University, told the New York Times. "We're looking at a classic strategy of building up tension."

In Crimea, Putin is slated to meet with security officials in the territory, and make an appearance at a children's summer camp.

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