Moscow will see any decision by the United States to provide Ukraine with lethal weapons as a threat to Russia's security, Russian Foreign Ministry spokesman Alexander Lukashevich said on Thursday.

Lukashevich was responding to calls in Washington and by Kiev for the United States to begin arming Ukraine to battle Russian-backed separatists advancing in the east.

Lukashevich also accused Kiev of using weapons that were having an effect similar to that of weapons of mass destruction in the conflict in east Ukraine.