Russian cruise missiles fired at Syria that the Defence Ministry said had reached their targets crashed in Iran, US officials said.
At least four missiles launched from the Caspian crashed as they flew over Iran, officials told CNN.
But Russian Defence Ministry spokesman Major General Igor Konashenkov said: "In contrast to CNN we do not talk with reference to anonymous sources but we show the launch of our rockets and the targets they struck."
"No matter how unpleasant and unexpected it is for our colleagues in the Pentagon and Langley, our strike yesterday with precision-guided weapons at ISIS infrastructure in Syria hit its targets."
On Thursday, U.S. Secretary of State John Kerry had a 30-minute telephone call with his Russian counterpart, Foreign Minister Sergei Lavrov, to express concern that Russia's targets in Syria were not related to Islamic State.