Tensions are also high in the Gulf following last month's attacks on vessels near the Strait of Hormuz, a vital oil shipping route, and Iran's downing of a USA drone.
Questioning the legality of the UK's move, Minister Zarif pointed out on Twitter that "Iran is neither a member of the EU nor subject to any European oil embargo".More news: Bank of Canada head expected to hold interest rates steady
After the incident Mohammad Javad Zarif, Iran's foreign minister, said the UK's action had set "a unsafe precedent and must end now".
General Amir Hatami added that this action "is against global norms and is a sort of piracy on the high seas".
Britain should be "scared" about Tehran's possible retaliation for the capture of an Iranian supertanker by Royal Marines in Gibraltar, the Fars semi-official news agency on Saturday reported an Iranian cleric as saying.More news: France says Javelin missiles found in Libya were 'unusable' - army ministry
"We have shown that we will never remain silent against bullying", said cleric Mohammad Ali Mousavi Jazayeri, warning of "an appropriate response" and mentioning Iran's shooting down of a U.S. drone last month. "She is heavy", they said in a tweet on Thursday.
Iran on Friday demanded that Britain immediately release the tanker, but Gibraltar's Supreme Court ruled that the vessel can be held for 14 more days.
It comes as Iran's foreign minister accused the United Kingdom of "piracy" for seizing and detaining the Grace 1 crude oil supertanker on Thursday.More news: Federal Reserve chairman signals cut in United States interest rates
It's now off Saudi Arabia's coast and a person with knowledge of the matter says BP's concern is that it could become a target if Iran seeks to retaliate for the seizure near Gibraltar - by British Royal Marines - of the tanker Grace 1 on July 4. And EU as a principle doesn't impose its sanctions on others.