With heightened tensions in the Gulf following Iran seizing a British-flagged oil tanker, the Stena Impero,  on Friday in the Strait of Hormuz, the Royal Navy is sending a nuclear-powered attack submarine to the region to bolster its force there.

Sources, according to the Express, said the Astute-class submarine would perform a purely defensive role. The Navy will use the submarine’s sophisticated covert electronic intelligence gathering equipment to safeguard British and international shipping. The submarine, as per the Sun, will listen in to Iranian communications before passing information back to its operational headquarters at Northwood, in North West London.

Tom Sharpe, a retired naval Commander, explained that the Royal Navy chose the Astute-class submarine because of the danger posed by Iran’s Yono-class midget submarines. Sharpe described the Yono midget submarine as a menace. “Often lurking just below the surface, they are armed with a couple of heavyweight torpedoes. These will kill a frigate and possibly even a carrier. There are always a couple at sea and they are hard to track and even harder to defeat,” he said.

Reports say the Royal Marines will also be deployed in the region, with some already on the ground. They have been authorized to use heavy-calibre machine guns, snipers and light anti-tank missiles to keep away Iranian forces. Meanwhile, the HMS Duncan, a Type 45 air-defence destroyer, is also headed for the Gulf to support the warship HMS Montrose that is already deployed in the Gulf.

The deployment of a nuclear submarine was discussed at the meeting of the Cobra emergency response committee after Iran’s Revolutionary Guards Corps (IRGC) seized the British oil tanker for allegedly violating international maritime rules.

British Foreign Secretary Jeremy Hunt said U.K. vessels “must and will be protected." During an emergency call with his Iranian counterpart Mohammad Javad Zarif, Hunt expressed extreme disappointment. “This has to be about actions, not words, if we are to find a way through. British shipping must and will be protected,” he said.

The Sun said the U.K. is also pushing for EU and UN sanctions to be reimposed on the Iranian regime after they were lifted in 2016 as part of a deal on Iran’s nuclear program.

Hamid Baeidinejad, Iran’s envoy to Britain, took to Twitter, saying “the U.K. 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 senstitive time in the region.”

Iran has warned the U.K. against further escalating the already tensed situation, saying that the oil tanker’s crew are safe.