Four Russian cruise missiles aimed at targets in Syria instead crashed in Iran, a US official said Thursday, declining to comment on whether there were any casualties.
The official, who spoke on condition of anonymity, said the missiles landed in Iran on Wednesday, but did not provide details about where they might have landed or whether they caused any damage.
Nor would the official say exactly what type of cruise missiles went down, except to say that they were among a salvo fired Wednesday from Russian warships in the Caspian.
The Russian Defense Ministry posted a graphic on its website showing 26 missiles overflying Iran and Iraq before striking inside Syria.
Russia has been conducting air strikes in Syria in defense of the embattled regime of President Bashar al-Assad since September 30.
The missile launches were in support of a major ground offensive by the Syrian army on several fronts in the war-torn country's west.
US Defense Secretary Ashton Carter on Thursday deplored the fact that Russian warships fired the cruise missiles "without warning."