Iran on Sunday urged Britain to contain “domestic political forces” intent on escalating tensions between the two countries following Iran’s seizure of a British-flagged oil tanker.

Britain has called Iran’s capture of the Stena Impero in the Gulf on Friday a “hostile act” and rejected Tehran’s explanation that it seized the vessel because it had been involved in an accident.

The “UK government should contain those domestic political forces who want to escalate existing tension between Iran and the UK well beyond the issue of ships. This is quite dangerous and unwise at a sensitive time in the region,” Iran’s envoy to Britain Hamid Baeidinejad said on Twitter.

“Iran however is firm and ready for different scenarios,” he said.

A day earlier British Foreign Minister Jeremy Hunt said Tehran’s actions showed “worrying signs Iran may be choosing a dangerous path of illegal and destabilizing behavior after Gibraltar’s legal detention of oil bound for Syria.”

The crew of the tanker seized by Iran’s Revolutionary Guards are all safe, the head of the Ports and Maritime Organization in Hormozgan Province told state TV on Sunday.

“All 23 crew members aboard the ship are safe and in good health in Bandar Abbas port,” Allahmorad Afifipour said.

Afifipour said that the seized tanker “risked maritime safety” in the Strait of Hormuz, through which almost a fifth of the world’s annual oil consumption passes. “We are required by regulations to investigate the issue … the duration of the investigation depends on the level of cooperation by the involved parties,” said Afifipour.

The seizure has heightened tension between Iran and Britain, which is a party to Iran’s 2015 multinational nuclear deal. The Daily Telegraph newspaper reported on Saturday that London was planning to target Iran with sanctions in the aftermath of the tanker seizure.

In a letter to the UN Security Council, Britain said the tanker was approached by Iranian forces in Omani territorial waters where it was exercising its lawful right of passage, and that the action “constitutes illegal interference.”

Stena Bulk, the vessel’s Sweden-based owners, said it is preparing a formal request to visit the crew, who are from India, Latvia, the Philippines and Russia. India has called on Iran to release the 18 Indian crew members.