The Revolutionary Guard of Iran has seized a Panamanian flagged tanker which was allegedly smuggling fuel (archived). The smuggling operation was apparently discovered after Revolutionary Guard boats responded to a distress call issued by the tanker. The ship was apparently being loaded with fuel from Iran for transit to foreign ships. This would mean the ship's seizure is a matter of Iranian law enforcement rather than a tit-for-tat response to foreign piracy conducted against ships carrying Iranian oil at sea.
At this time the foreign party receiving smuggled Iranian oil has yet to identify itself.