"As for the strengthening of our western borders because of the actions adopted by NATO countries... this needs to be considered separately, I ask you to prepare a report," Putin told Defense Minister Sergei Shoigu during a televised meeting of Russia's Security Council.

NATO countries have deployed thousands of troops to central and eastern Europe in response to Russia's "special military operation" in Ukraine and Moscow has demanded NATO pull back its troops in the east.

NATO members Poland and the three Baltic states share a common border with Russia. Ukraine borders several others: Hungary, Romania and Slovakia.