The United States has intercepted an order from an Iranian official instructing militants in Iraq to attack US interests in Baghdad in the event Washington launches a military strike in Syria, The Wall Street Journal reported on Thursday.

The US embassy in Baghdad was a likely target, according to unnamed US officials. The Journal said the officials did not describe the range of potential targets indicated by the intelligence.

In addition, the US State Department issued a warning on Thursday telling US citizens to avoid all but "essential" travel to Iraq.

The Journal reported that the Iranian message was intercepted in recent days and came from the head of the Revolutionary Guards' Qods Force.

The department said that numerous insurgent groups, including al-Qaida's Iraq affiliate, remain active and "terrorist activity and sectarian violence persist in many areas of the country at levels unseen since 2008".

Reuters