SIMFEROPOL, Ukraine — Ukraine accused Russia of a “military invasion and occupation” today, saying Russian troops have taken up positions around a coast guard base and two airports on its strategic Crimea peninsula.

Russia kept silent on those accusations but confirmed that armored vehicles from its Black Sea Fleet were moving around Crimea for “security” reasons as the crisis deepened between two of Europe’s largest countries.

Any Russian military incursion in Crimea would dramatically raise the stakes in Ukraine’s conflict, which saw pro-Russian President Viktor Yanukovych flee last weekend after three months of anti-government protests. Yanukovych vowed today to “keep fighting for the future of Ukraine,” though he called any military action “unacceptable.”

Moscow has vowed to protect Russian-speaking Ukrainians in Crimea, where it has a major naval base, and Ukraine and the West have warned Russia to stay away. Russia did not confirm its troops were involved in today’s action in Crimea, which would be a major escalation.