Western officials had suspected a Russian cargo vessel was carrying helicopter gunships and anti-aircraft systems to Syria. Russian shipowner Femco denied the allegations.
U.S. Secretary of State Hillary Clinton last week accused Moscow of arming Syrian forces, who are suspected of committing war crimes against its people during the 15-month conflict.
Moscow has threatened to use its veto at the U.N. Security Council to block any formal resolution against Syria, one of Russia's top arms customers. Nevertheless, the Foreign Ministry warned its citizens to avoid travel to the country.
"The Russian Foreign Ministry again reiterates its recommendation to Russian citizens not to travel to Syria either for tourism, or in general," spokesman Alexander Lukashevich was quoted by RIA Novosti as saying.
Russian military officials this week denied reports it was sending navy ships to the Syrian port of Tartus.
Meanwhile, U.S. and Arab officials told The New York Times on condition of anonymity that CIA officers were assessing which factions of the Syrian opposition would receive weapons from Arab allies.
Syrian maintains much of the conflict is the results of defensive measures against domestic terrorists supported by outside groups.
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