Iranian leaders have summoned the British ambassador as Tehran fumes over Britain's Thursday seizure of an Iranian tanker believed to be violating the European Union sanctions by providing crude oil to the Syrian regime.

British Royal Marines supported the authorities in Gibraltar in taking the vessel amid evidence that it was trying to circumvent the EU sanctions on the Syrian regime. A senior Spanish official said the operation was requested by the United States.

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The Iranian vessel was believed to be headed to the Baniyas Refinery in Syria, a government-owned facility under the control of Syrian President Bashar Assad and subject to the EU’s Syrian Sanctions Regime.

The Iranian state-run news agency called the situation “an illegal seizure of an Iranian oil tanker” while an Iranian foreign ministry spokesman called the actions a “form of piracy” – prompting the UK’s foreign office to dismiss the claims as “nonsense.”

Iranian Foreign Ministry spokesman Abbas Mousavi wrote in a tweet that British Ambassador Rob Macaire was summoned over the “illegal interception” of the ship and later said that the seizure was “odd and destructive.”

“It can cause an increase in tensions in the region,” he said in a live telephone interview on state television Thursday night.

U.S. National Security Adviser John Bolton, meanwhile, welcomed Britain's move, saying the seizure was “excellent news.”

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“America & our allies will continue to prevent regimes in Tehran & Damascus from profiting off this illicit trade,” Bolton said in a tweet.

The vessel carrying Iranian oil likely had over just over 2 million barrels of Iranian crude oil, according to the data firm Refinitv.

The seizure of the tanker comes amid heightened tensions in the Middle East, particularly between Washington and Tehran, with the latter officially violating the 2015 nuclear deal this week by breaking through the deal put on its stockpile of low-enriched uranium – and has pledged to boost its enrichment on Sunday.

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The Iranian regime also shot down an American drone, prompting the Trump administration to consider military strikes on the country. The strikes were scrapped last minute by President Trump.

The Associated Press contributed to this report.