"We are calling on all our partners to once again think thoroughly before taking this very dangerous step,” he told reporters after a G8 summit in Northern Ireland.
"Europe wants to send arms to these people? And what happens then to these arms? Who will control in whose hands and where they will end up? Maybe in Europe?"
He also rejected US and European claims that Syria's government had used chemical weapons.
"We do not have facts pointing to the use of such weapons by the Syrian government," Putin said.
"I assure you that, by far, not all G8 members believe that (chemical arms) were used by the Syrian army. Some agree with our opinion that there is no such data."
About Russia’s military contracts with Syrian government and shipment of arms to Damascus Putin said, "If we conclude such contracts, then we will deliver on such contracts,"
"We are supplying arms to the legitimate government in accordance with legal contracts,” he added.
US, Israel and several Western countries have been pressing Russia not to go through with a promised delivery of S-300 missiles to the Syrian government.