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. 

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, adding that Iran is firm and ready for different scenarios.

Iranian Foreign Minister Mohammad Javad Zarif said on the same day that only "prudence and foresight" could alleviate tensions between his country and Britain.

According to the head of the Ports and Maritime Organization in Hormozgan Province, the crew of the tanker seized by Iran's Revolutionary Guards are all safe.

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

In response, British Junior Defense Minister Tobias Ellwood said on Sunday that Britain is looking into a series of options to respond to Iran's move. 

"Our first and most important responsibility is to make sure that we get a solution to the issue to do with the current ship, make sure other British-flagged ships are safe to operate in these waters and then look at the wider picture," he told Sky News.

Asked about the possibility of sanctions, he said: "We are going to be looking at a series of options ... We will be speaking with our colleagues, our international allies, to see what can actually be done."

Meanwhile, warnings can be heard from the UK side that Britain should not be dragged into a conflict as it was in Iraq. 

Britain should not become the "messengers" for U.S. President Donald Trump over Iran's seizure of a UK-flagged tanker, said Richard Burgon, Justice spokesman for the opposition Labour Party on Sunday.

"I think we can play a very positive role in this ... Our role is to speak up for conflict resolution, de-escalation, the nuclear deal," Burgon noted, "but what we don't want to do is end up being the messengers or sidekicks of Donald Trump."

The president pulled his country out of the nuclear agreement with Iran last year and reimposed and tightened sanctions on Iran's oil and banking sectors. 

Afifipour said 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."

British Foreign Minister Jeremy Hunt on Saturday 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."

Stena Bulk, the vessel's Sweden-based owner, 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. 

Tehran for weeks has vowed to retaliate for the seizure by Royal Marines of the tanker Grace 1 carrying Iranian oil near Gibraltar on July 4 which was suspected of violating sanctions on Syria. 

"The Revolutionary Guards responded to Britain's hijacking of the Iranian tanker," Iranian parliament speaker Ali Larijani told a parliament session aired live on state radio.