Iran’s Foreign Ministry has summoned Britain’s ambassador to the country after British forces seized an Iranian oil tanker in the Strait of Gibraltar.

Rob Macaire was summoned to the ministry on Thursday, hours after reports emerged that the vessel had been boarded by British Royal Marines and impounded.

Later in the day, Iran's Foreign Ministry spokesman Abbas Moussavi took part in an interview with the Islamic Republic of Iran Broadcasting (IRIB)’s News Network, saying, "We declared to the ambassador that this move amounts to strange unconventionality, because the sanctions that they have announced are not based on the Security Council [resolutions] and the Islamic Republic of Iran does not accept this measure (seizure of the tanker).”

The Iranian diplomat further stated that the Spanish Foreign Ministry has confirmed that the move was made at the request of the US and that the seizure amounted to “implementation of a type of extraterritorial sanctions despite the fact that the European Union has invariably been against such bans.”

Moussavi said that Iran denounces the seizure as "a destructive step," which contributes to further escalation in regional tensions.

Citing a Spanish source, France 24 reported earlier that the tanker had been seized by Britain at the US request.

Later in the day, acting Spanish Foreign Minister Josep Borrell said Gibraltar detained the supertanker Grace 1 after a request by the United States to Britain.

Borrell was quoted by Reuters as saying that Spain was looking into the seizure of the ship and how it may affect Spanish sovereignty as it appears to have happened in Spanish waters.

Spain does not recognize the waters around Gibraltar as British.

Britain's Foreign Office did not respond to a request for comment.

Experts believe that the measure taken by the British government in seizing the Syria-bound Iranian tanker is illegal and can have serious consequences for the government in London.

Since Iran's tanker was carrying fuel and oil to Syrian people for solely humanitarian purposes, the measure taken by the British government is not only illegal, but also inhumane.

Iran and Syria enjoy vast commercial and trade ties and under the international law, Britain has no right to interfere in their relations.

The US has avowed an intention to reduce Iran’s oil exports to “zero” as part of the sanctions that it reinstated after leaving a multilateral nuclear deal with Iran last year. Both Washington’s withdrawal from the deal and its reintroduction of the sanctions came while the accord has been ratified in the form of the United Nations Security Resolution 2231.

Europe has suspended its trade with Iran, knuckling under the sanctions, despite being obliged by the agreement to safeguard Iran’s business interests.

Earlier this week, Iran’s Foreign Minister Mohammad Javad Zarif reminded the deal’s European partners that they had undertaken 11 commitments to the country under the nuclear accord.

These, he added, include Iran’s oil sales, secure financial returns from the sales, and investment in Iran, as well as facilitation of transport, aviation, and shipping activities involving the country.

Observers deem the seizure of the tanker on Washington’s apparent orders to be another instance of the European states’ non-commitment to the deal.