Tensions in the Arabian Gulf reached the boiling point Friday with Iran seizing a British-flagged oil tanker in the Strait of Hormuz for allegedly violating "international laws." Iran's Revolutionary Guard also seized a second tanker but later set it free.

Oil prices rose after the reports of the seizure of the first ship during afternoon trading in the United States. About a third of the world's oil exports pass through the Strait of Hormuz and an escalation of the tensions could drive up oil prices and further apply the brakes on the global economy, which is already slowing down amid a trade war between the U.S. and China.

The seizure of the Stena Impero is seen as a Iran's retaliation for the Gibraltar detaining an Iranian tanker earlier this month over suspicions that it was carrying oil to Syria, which is under European Union sanctions. Iran has denied that the crude was meant for Syria.

British Foreign Secretary Jeremy Hunt, warned Iran of serious consequences if the vessel was not released. "We will respond in a way that is considered by robust. And we are absolutely clear that if this situation is not resolved quickly, there will be serious consequences," Hunt said in comments late Friday night.

iran us oil tanker A picture obtained by AFP from Iranian News Agency ISNA on June 13, 2019 reportedly shows fire and smoke billowing from Norwegian owned Front Altair tanker said to have been attacked in the waters of the Gulf of Oman. Photo: -/AFP/Getty Images

Erik Hanell, the chief executive of Stena Bulk, the operator of the Stena Impero, said the ship has 23 crew on board, who are of Indian, Russian, Latvian and Filipino nationality, its operator  “There have been no reported injuries and the safety and welfare of our crew remains our primary focus,” he said. Iran said the crew members will remain on board till it finishes the investigation.

The Stena Impero’s Swedish owner Stena AB said a hostile action had preceded the vessel’s change of course Friday. In a statement the company said the vessel had been approached by an unidentified small craft and a helicopter during transit of Strait of Hormuz while it was in international waters.

However, Iranian news reports said the Stena Impero was in involved in an "accident’ with an Iranian fishing boat and ignored a distress call. The vessel is now docked at Iran’s Bandar Abbas port with all its 23 crew members onboard.

“On Friday, a British tanker by the name of Stena Impero while passing through the Strait of Hormuz was seized by the IRGC due to violating international regulations,” the IRG confirmed in a statement. “After it was seized, it was transferred to Iranian shores to undergo legal procedure.

A second vessel, the British-operated, Liberian-flagged Mesdar was also intercepted by the IRG, 40-minutes after the course shift by Stena Impero. The vessel was held for some time then allowed to continue. The British-owner of Mesdar said armed personnel boarded the vessel but later it was allowed to proceed. Norbulk Shipping UK in a statement said communication has been re-established with the Mesdar and the captain confirmed that armed guards had left and the vessel is free to continue the voyage. The vessel was on its way from China to Saudi Arabia when it was halted.

It's believed that HMS Montrose (Type-23) was dispatched to aid Stena Impero, but it was late. It is the same Royal Navy ship that had warned off Iranian boats that had tried to "impede" another British tanker last week.

A British Government spokesman said UK vessels have been advised to stay out of the area of the Strait of Hormuz for an "interim period." “As the Foreign Secretary has said, our response will be considered and robust and there will be serious consequences if the situation is not resolved,” he said.

U.S. President Donald Trump said Iran was showing its true colors and warned that it was in big trouble. Tensions with Iran have increase after the country broke the terms of the 2015 nuclear deal that the United States abandoned last year, and restarted its nuclear enrichment program.