MOSCOW, April 16 (Xinhua) -- The U.S.-led missile strikes on Syria prevented experts of the Organization for the Prohibition of Chemical Weapons (OPCW) from entering Douma to investigate an alleged chemical weapons attack, a senior Russian diplomat said Monday.

Earlier in the day, the British delegation to the OPCW tweeted that the "OPCW arrived in Damascus on Saturday. Russia & Syria have not yet allowed access to Douma. Unfettered access essential. Russia & Syria must cooperate."

Russian Deputy Foreign Minister Sergei Ryabkov denied the accusation and said it was Britain's speculation.

He said the OPCW experts did not visit Douma due to a lack of permission from the United Nations following the missile strikes launched by the United States, Britain and France on Saturday, without waiting for the results of the investigation.

Kremlin spokesman Dmitry Peskov also criticized the accusation that Russia is blocking the OPCW's access to the site where a Syrian rebel group accused Syrian government forces of alleged use of toxic substances in the formerly rebel-held Douma near the capital Damascus on April 7, which the Syrian government denied.

Peskov said the accusation is groundless and Russia always advocates an impartial investigation into the incident.

The Kremlin reiterated that the recent U.S.-led missile strikes were an "aggression" against Syria and violated international law.

"The U.S. tries to undermine the credibility (of) the (OPCW) Fact-finding mission in Syria even before it arrives at Douma. Russia confirms its commitment to ensure (the) safe(ty) and security of the mission and will not interfere in its work," the Russian Embassy in The Netherlands tweeted.