Britain is set to send a third warship to the Gulf amid a tense stand-off with Iran.

The Ministry of Defence said Type 23 frigate HMS Kent would deploy to the Gulf later this year as part of Operation Kipion, the UK's mission in the region, after days of threats to British shipping.

Type 23 frigate HMS Montrose is currently in the region but is due to undergo maintenance and crew change, with Type 45 destroyer HMS Duncan travelling to the Gulf to take over.

Kent will in turn take over from Duncan later this year to ensure an 'unbroken presence' in the region.

The MoD insists that the movements are 'long-planned' and not an escalation, but they come after weeks of tension in the Gulf which heightened further when Britain seized an Iranian tanker off Gibraltar two weeks ago.

Iran's supreme leader Ayatollah Ali Khamenei said today that 'vicious' Britain's seizure of the Iranian oil tanker was 'piracy.'

The Ministry of Defence said Type 23 frigate HMS Kent (pictured with its specifications) would deploy to the Gulf later this year

Kent (pictured in Britain in 2016) take over from Duncan later this year to ensure an 'unbroken presence' in the region

The tanker RFA Wave Knight will also join the British Gulf fleet at the start of August, delivering food, fuel, water and essential supplies to other Navy vessels.

Approximately 1,200 personnel are deployed in the region along with seven Royal Navy and support ships, including Montrose and Duncan.

The support ships include four Mine Counter Measures Vessels: HMS Ledbury, Blyth, Brocklesby and Shoreham.

Defence sources have said that Britain is willing to take 'precautionary measures' to protect freedom of navigation in the Gulf.

Britain was dragged into the Middle East stand-off after Royal Marines seized the supertanker Grace 1 off Gibraltar on July 4, saying it was heading for Syria in violating of EU sanctions - a claim which Iran has denied.

Tehran has threatened to retaliate, and Britain said last week that the Montrose was forced to confront three Iranian vessels who targeted a UK-flagged tanker.

Earlier today, it was claimed that an unmanned Iranian bomb boat was discovered lying in wait for the Duncan in the Red Sea.

The remote-controlled 'Blowfish' was reportedly spotted by Saudi forces in the destroyer's path as it headed south from the Suez Canal to protect Gulf shipping lanes.

The small vessel was laden with explosives, enough to blow a hole in the side of the destroyer, and steered from up to four miles away, sources told the Mirror.

Former naval officer Simon Warrington said: 'The threat from the Houthis, who as Iran's proxy militia do Tehran's dirty work, is very real.'

The Ministry of Defence declined to comment.

The Royal Navy's most modern warship was dispatched the the Persian Gulf over the weekend to protect British-flagged oil tankers from Iran

A vessel known as a Blowfish was reportedly discovered by the Saudi navy lurking in the path of HMS Duncan as it made its way south through the Red Sea towards the Gulf

The Blowfish bomb boat was reportedly discovered in the Red Sea where Iranian-backed Houthi rebels have been known to deploy small vessels laden with explosives in the past

Fears of threats to Gulf shipping have been heightened after six tankers were hit by explosions in the space of a month.

A UAE investigation found four mysterious sabotage attacks on May 12 were linked to a 'state actor' but did not name Iran.

The attacks were carried out with limpet mines and were 'part of a sophisticated and coordinated operation', the report found.

The tanker attacks inflamed an already tense Middle East stand-off and prompted the U.S. to bolster its military presence in the region.

Matters worsened just four weeks later when another two ships were hit by explosions in the Gulf of Oman.

Forty-four sailors were forced to abandon their ships amid a huge fireball on the MT Front Altair and another blast on the Kokuka Courageous.

America again blamed Iran, releasing a video which purported to show Iranian revolutionary guard forces removing an unexploded limpet mine from one of the ships.

Small explosive-packed vessels, including suicide boats, have been deployed by Iran-linked Houthi rebels in the past.

Similar water-based improvised explosive devices (WBIEDs) have been discovered by Saudi Arabia and the UAE in recent years.

In January 2017, two Saudi sailors were killed after Houthi explosive vessels blew up at the side of a frigate.

America has also bolstered its military presence in the region after Tehran lashed out at crippling sanctions as a result of the crumbling Iran deal, with a series of attacks on oil tankers in recent months.

EU nations are desperately trying to salvage the Obama-era agreement, as Iran's top diplomat warned yesterday the U.S. was 'playing with fire.'

The U.S. has sent thousands of troops, an aircraft carrier, nuclear-capable B-52 bombers and advanced fighter jets in recent weeks.

British Foreign Secretary Jeremy Hunt said there was still a 'small window to keep the deal alive' as EU foreign ministers met in Brussels on Monday (Hunt speaking to the Spanish foreign minister Josep Borrell)

U.S. Navy's Amphibious dock landing ship USS Harpers Ferry, left, and fleet replenishment oiler ship USNS Tippecanoe sail alongside amphibious assault ship USS Boxer during a replenishment-at-sea, in the Gulf of Aden earlier this month

Iran has said President Donald Trump's strict sanctions over alleged breaches to the 2015 Iran nuclear deal amounts to an 'economic war.'

That deal hangs in the balance - Trump announced the U.S. withdrawal in May last year and the Iranians have been increasing their uranium enrichment - but EU member states are clinging on.

Iran announced last week that it had enriched uranium past the 3.67 percent limit set by the nuclear deal, and has also surpassed the 300-kilogram cap on enriched uranium reserves.

The 28 EU foreign ministers have insisted that Tehran's surpassing of uranium enrichment thresholds set by the deal did not necessarily condemn the agreement.

The EU currently has few direct measures for offsetting U.S. economic sanctions against Tehran that have savaged the country's economy, and the bloc faces U.S. threats to target any EU companies that attempt to trade with Iran.

Noting that Iran was 'still a good year away' from potentially developing a nuclear bomb, British Foreign Secretary Jeremy Hunt said there was still a 'small window to keep the deal alive.'

President Donald Trump (right) has slapped heavy sanctions on Iran after it says Tehran breached the 2015 JCPOA, President Hassan Rouhani has engaged in heated rhetoric with Trump after attacks on tankers and a US drone

Tehran said Sunday it was ready to negotiate with the United States if Washington lifts the economic sanctions.

President Hassan Rouhani's official website quoted him as saying, 'The moment you stop sanctions and bullying, we are ready to negotiate.'

The Iranian Foreign Minister Mohammad Javad Zarif said on Monday: 'We are not about to develop nuclear weapons. Had we wanted to develop nuclear weapons, we would have been able to do it (a) long time ago.'

Zarif's comments came as the U.S. imposed unusually harsh restrictions on his movements during a visit to the United Nations in New York.