An Iranian official has said a British oil tanker should be seized, if a detained Iranian ship is not released.
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, at the request of the Gibraltar government.
But Iran's Foreign Ministry condemned the move as illegal and accused the UK of acting at the behest of the United States. Spain's acting foreign minister also said, on Thursday, that the seizure of the ship was at the US's request.
On Friday, a senior Iranian lawmaker said the seizure of tanker was proof the UK "lacks honour" and takes orders from the US.
Mostafa Kavakebian, who leads the Iran-UK parliamentary friendship group, tweeted that the seizure was "a form of piracy and illegal hostility towards Iran".
The UK Foreign Office dismissed claims of piracy as "nonsense".
