Russian envoy to NATO, Dmitry Rogozin, said on Thursday that there will be a firm response from Moscow to NATO's decision to expel two Russian diplomats from its headquarters.

    Rogozin confirmed that two officials from the Russian mission to NATO have had their accreditation canceled.

    "The response will be clear and tough," Rogozin told reporters in Brussels.

    The two Russian officials were declared personae non grata by NATO for alleged involvement in espionage. But Rogozin denied that they were spying.

    "We regard the decision taken by the alliance as a provocation. Its timing is in no way accidental," said the Russian mission in a statement.

    "It appears that some members of NATO are discontent with the way Russia-NATO relations have recently been developing, and they provoke an international scandal on purpose, going all out in their attempt to disrupt Russian re-engagement with the alliance along with a reset in relations between Russia and the United States," said the statement.

    The two diplomats -- Viktor Kochukov, a senior counselor for political affairs, and Vasily Chizhov, an attache and security officer -- were declared unwelcome by NATO on Wednesday, the same day when NATO and Russia resumed formal talks after a freeze of eight months.

    "The fact that this announcement was made immediately after the first formal NATO-Russia Council meeting at the level of ambassadors since the freeze of NRC work in August 2008, where questions relating to the upcoming meeting of ministers of foreign affairs of NRC member states were discussed, creates a tense atmosphere and sets the wrong tone for the whole process of resuming Russia-NATO cooperation," said the statement.

    "This decision might call into question this very (NRC) meeting, which is aimed at re-launching the whole process of re-engagement in NATO-Russia Council activities," it added.

    The statement said the NATO decision is regrettable and that Russia is considering possible response measures.

    The statement echoed a Russian Foreign Ministry statement, which labeled the NATO decision as provocation.

    "We have learned about a provocative act against two staff members of the Russian mission at NATO, whom the alliance security service would like to expel from Brussels under a far-fetched pretext and without any clear explanations," said the ministry in a statement.

    "We urge all NATO members to think about the consequences of what happened. We will certainly make our own conclusions from this provocation," it said.

    It is believed that the two diplomats were accused of involvement in a spy scandal, in which a former Estonian diplomat, Herman Simm, allegedly passed on NATO secrets to Moscow. Simm was jailed for more than 12 years in February.

    One of the diplomats to be expelled, Vasily Chizhov, is the son of Russia's ambassador to the European Union, Vladimir Chizhov.

    NATO has refused to comment on the expulsion.