Nebenzia said this during a meeting of the UN Security Council.
According to him, the hidden supply of weapons to different regions through third countries "further distorts the picture of arms flows in the world and reduces transparency in this area."
He expressed regret that Western countries do not combat such violations and encourage them.
"The United States and its allies are putting pressure on third countries, demanding that they violate such agreements with Russia and other states in the interests of increasing arms supplies to Kiev," TASS quoted the diplomat as saying.
Earlier, Nebenzia said that Russia is receiving more and more evidence that Western countries are directly involved in the Ukrainian conflict.