Moscow said yesterday a mortar fell on the embassy compound in the Syrian capital on Sunday without causing damage and blamed forces battling President Bashar al-Assad and their "outside sponsors" for the shelling.
"We await a clear standpoint on this terrorist act from all members of the international community, including regional actors," Russia's foreign ministry said in a statement.
"What is needed is not just words, but concrete action."
The United States says Russia -- one of the few remaining allies of Assad -- is deploying personnel and military hardware to Syria, sparking fears Moscow is getting ready to fight alongside government forces.
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Yesterday, two US officials told AFP that Russia has deployed 28 ground attack and fighter planes at an airfield in the western Syrian province of Latakia.
One of the officials added there were also about 20 Russian combat and transport helicopters at the base. The officials spoke on condition of anonymity.
But Russia contends any such support falls in line with existing defence contracts.
Moscow and Washington on Friday launched military talks on the four-year conflict that has claimed nearly 250,000 lives.