British Royal Marines helped officials in Gibraltar to seize the super-tanker Grace 1 on Thursday, after it was suspected of carrying oil from Iran to Syria, in breach of EU sanctions.
Iran later summoned the British ambassador in Tehran to complain about what it said was a "form of piracy".
Mohsen Rezaei said Iran would respond to bullies "without hesitation".
Mr Rezaei - a member of a council that advises the Supreme Leader, Ayatollah Khamenei - said, in a tweet: "If Britain does not release the Iranian oil tanker, it is the authorities' duty to seize a British oil tanker."
The BBC has been told a team of about 30 marines, from 42 Commando, were flown from the UK to Gibraltar to help detain Grace 1 and its cargo.
Gibraltar said there was reason to believe the ship was carrying Iranian crude oil to the Baniyas Refinery in the Syrian Mediterranean port town of Tartous.
The territory's Supreme Court has ruled the tanker can be detained for a further 14 days, Gibraltar's attorney general said.
Iran's Foreign Ministry condemned the initial seizure of the vessel as illegal and accused the UK of acting at the behest of the United States.
The UK Foreign Office dismissed claims of piracy as "nonsense".
Spain's Acting Foreign Minister Josep Borrell said, on Thursday, Spain - which disputes British ownership of Gibraltar - was studying the circumstances of the action, but said it followed "a demand from the US to the UK".
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