A senior Ukrainian security official says his country is open to placing a ballistic missile-defense system in Ukraine to ward off the potential risk of attacks from Russia.

Oleksandr Turchynov, the head of Ukraine's National Security Council, told Ukrinform news agency Wednesday that Russia has become an increased threat since annexing Crimea and increasing its military presence there.

Turchynov's comments mark an intensification of hostile rhetoric between Russian and Ukraine. Kiev accuses Russia of providing weapons and manpower to the armed separatists now controlling swaths of eastern Ukraine.

NATO's U.S.-led missile-defense plans envisage deploying elements of the missile shield around Europe for what it says would be defense against Iran. Moscow sees this as a threat to its nuclear deterrent and has threatened countermeasures.