LONDON, June 11 (Reuters) - Russia's foreign ministry said on Saturday that Moscow's response to a build up of NATO forces in Poland will be proportionate, Interfax news agency reported citing a Russian diplomat.

"A response, as always, will be proportionate and appropriate, intended to neutralise potential threats to the security of the Russian Federation," Interfax quoted Oleg Tyapkin, the head of a foreign ministry department in charge of Russian relations with Europe.