Ukraine's security council chief has accused Russia of a massive military buildup near Ukraine's border that raises the threat of an invasion.

Andriy Parubiy, secretary of Ukraine's National Security and Defense Council, told Wednesday's briefing in Kiev that Russia has deployed more than 80,000 troops close to the border, creating the "threat of a full-scale invasion from various directions."

In Moscow, Deputy Defense Minister Anatoly Antonov denied a military buildup on the Russia-Ukraine border. He also said Moscow has accepted a request that Ukraine made Tuesday to conduct a surveillance flight over the Russian territory to make sure there is no threat.

Russian forces have secured control over Ukraine's Crimean Peninsula, and President Vladimir Putin says Moscow is ready to "use all means" to protect Russian speakers in eastern Ukraine.