BRUSSELS — After the annexation of the Crimean Autonomous Republic of Ukraine to Russian territory in a violation of international law, Russia continues to steadily increase its number of troops on the eastern border of Ukraine, in a move, which has concerned the West.

Closely following the recent developments, NATO has issued a "harsh warning" to Moscow in regards to the situation in Ukraine.

"NATO is very concerned about a Russian military build-up on Ukraine's borders and has all plans in place to defend members of the alliance", NATO Secretary-General Anders Fogh Rasmussen said on Tuesday.

"All NATO allies can be assured of our determination to provide effective defence ... We have all plans in place to provide effective defence of our allies," he said, adding that the Western military alliance was discussing with Kiev how it could enhance its support for non-NATO member Ukraine.