April 14 (Reuters) - Finland's embassy in Moscow has received a letter containing an unknown powder and has reported the matter to the Russian authorities, Russian foreign ministry spokeswoman Maria Zakharova said on Friday. "We can confirm such an appeal from the embassy of Finland to the Russian foreign ministry, according to which three identical envelopes addressed to the military attache and his aides were delivered on April 13 to the diplomatic mission's mailbox," she said. See here for a complete list of exchanges and delays