Iran's Grace 1 tanker off the coast of Gibraltar last week.
Iran says Britain is playing "a dangerous game" as the country demands the immediate release of an oil tanker seized by Royal Marines off the coast of Gibraltar.
The Iranian supertanker, the Grace 1, was seized last week as it was believed to delivering oil to Syria in breach of EU sanctions.
A spokesman from Iran's foreign ministry told the semi-official news IRNA: "This is a dangerous game and has consequences.
"The legal pretexts for the capture are not valid... the release of the tanker is in all countries' interest."
The comments come after the Ministry of Defence (MOD) announced a Royal Navy warship drove off three Iranian boats in the Strait of Hormuz.
The MOD said the boats, believed to be from the Iranian Revolutionary Guard Corps, were trying to stop a British tanker.
A UK Government spokesman said they were "concerned" by the incident and called on Iran to "de-escalate"
Iran denied the claims but did previously warn Britain of "consequences" for seizing Grace 1.
Police in Gibraltar have arrested the vessel's captain and chief officer.
Earlier this week, a US general called for the creation of an international military coalition to safeguard the Gulf's waters.
Tensions between the US and Iran have been heightened since President Donald Trump pulled the US out of a nuclear deal with Iran and reinstalled sanctions.