Several of the cruise missiles that Russia fired at Syrian targets landed instead in Iran, say US defence officials.
It is unclear whether the missiles, launched from Russian ships in the Caspian Sea, caused any significant damage in Iran. One official said the number of missiles that went off course was four.
The Russian government said on Wednesday it launched 26 cruise missiles, hitting targets in the Syrian provinces in the north and north-west. It made no mention of any missiles going astray. The missiles’ intended flight paths took them over Iran and Iraq.
The missile attack was part of an expanding Russian military campaign in Syria that has deepened the divide between Moscow and Washington over how to approach the Syrian civil war and the presence there of Islamic State fighters.
The missiles also have added a new layer of uncertainty to efforts by the Pentagon to ensure the safety of US and coalition pilots who are flying daily in Syria airspace. Russia is also flying attack and reconnaissance missions over Syria.
Russia says its intervention is aimed at helping the Syrian government defeat the Islamic State group, but local activists and US officials say the strikes have also targeted Western-backed rebels and have had the effect of propping up the government of President Bashar Assad.