The US accuses Iran of being behind a drone attack on a chemical tanker in the Indian Ocean.
Saturday's attack on Chem Pluto resulted in a fire, but no injuries were reported.
Although Iran has not commented on the attack, the US military said the “unilateral attack” was carried out by an “Iran-launched drone.”
It is said to be the first time that the US has accused Iran of directly targeting a ship. It is also believed to be the furthest attack undertaken from Iran.
Yesterday it accused Iran of supporting Houthi rebels in Yemen who have attacked merchant ships in the Red Sea.
The allegations come as Iran has threatened to close the Strait of Gibraltar and the Mediterranean if Israel and its allies continue to commit “crimes” in Gaza.
Iran, which has backed Hamas, accused the United States and other Western states of supporting Israel's alleged war crimes during its ground offensive in the Gaza Strip, which has left more than 20,000 people dead since October 7.
“You will soon be waiting for the closure of the Mediterranean, the Strait of Gibraltar and other waterways,” Brigadier General Mohammad Reza Naqdi, a senior member of the country’s Islamic Revolutionary Corps, said on Saturday.
The Iran-aligned Houthi group based in Yemen has attacked several merchant ships passing through the Red Sea in retaliation for Israel's brutal attack on the Gaza Strip, disrupting global trade and forcing some shipping companies to change their routes.
The White House said Friday that Iran was “deeply involved in the planning of these attacks.”
“You will soon be waiting for the closure of the Mediterranean, the Strait of Gibraltar and other waterways,” said Brigadier General Mohammad Reza Naqdi, a senior member of the country’s Islamic Revolutionary Corps
The Strait of Gibraltar and the Mediterranean are waterways that carry up to a fifth of the world's maritime trade
Over 20,000 people have died in Gaza as a result of Israel's ground offensive against the enclave
While Iran does not have direct access to the Mediterranean itself and it was not clear how the Guard might try to seal it off, Iran-backed proxies in Lebanon and Syria have access to these waterways, which carry about a fifth of the world's maritime trade .
Naqdi spoke of “the birth of new resistance forces and the closure of other waterways.”
“Yesterday the Persian Gulf and the Strait of Hormuz became a nightmare for them, and today they are trapped… in the Red Sea,” Naqdi added.
National Security Council spokeswoman Adrienne Watson told CNN that the US has intelligence indicating Iran provided a surveillance system essential to the attacks.
“Iran has the choice of providing or withholding this support, without which the Houthis would find it difficult to effectively detect and attack commercial vessels navigating shipping routes through the Red Sea and Gulf of Aden,” Watson said.
While Iran does not have direct access to the Mediterranean itself and it was not clear how the Guard might try to close it off, Iran-backed proxies in Lebanon and Syria have access to these waterways
“The tactical intelligence provided by Iran has been crucial to the Houthi attacks on maritime vessels since the group began attacks in November,” it added.
However, Iran's deputy foreign minister rejected claims that Iran was involved in the Houthi attacks.
“The (Houthi) resistance has its own tools… and acts in accordance with its own decisions and capabilities,” Iranian Deputy Foreign Minister Ali Bagheri told the country's Mehr news agency.
“The fact that certain powers such as the Americans and the Israelis are suffering attacks from the resistance movement… should in no way call into question the real strength of the resistance in the region,” he added.
The Houthis have been fighting against the Yemeni government since 2014, occupying large areas of land and being supported by Iran.
Following Israel's retaliatory offensive against the Gaza Strip, the group's leaders declared war on Israel and launched several attacks against Israeli cities, even though they were thousands of kilometers away.
Iran has repeatedly warned that Israel's war against Hamas will soon expand. Last month, Iranian Foreign Minister Hossein Amir-Abdollahian said the intensity of the war made its expansion “inevitable.”
The country's president, Ebrahim Raisi, said earlier that Iran sees it as “its duty to support the resistance groups,” but stressed that they are “independent in their opinions, decisions and actions.”
The UK and its allies will not allow the Red Sea to become a no-go zone for shipping and will step up efforts to combat Iran's “malign influence”, cabinet ministers said.
Defense Secretary Grant Shapps said the UK was determined to deter attacks by an Iran-backed group in Yemen on ships using the vital trade route.
And Foreign Secretary Lord Cameron said Tehran needed to receive an “incredibly clear message” that its activities would not be tolerated.
Mr Shapps told the Sunday Times: “We are committed to protecting British interests – ships flying the British flag, carrying British sailors or carrying goods destined for our shores.”
“We have seen the disruption the terrorist attacks have caused – major operators such as Maersk and BP are avoiding the region.”
“We cannot allow any maritime area to become a restricted area, especially such an important route.” But beyond that, we must work for a safer world.
“The spate of illegal attacks poses a direct threat to international trade and maritime security.”
“The rules-based global order means we must remain committed to deterring these attacks to protect the free flow of global trade, and I firmly believe the UK will remain a key player in this.”
Foreign Secretary Lord Cameron said Yemen's Houthi rebels, who have attacked cargo ships on the busy trade route, were just one of the groups supported by Iran, including Hamas.
The Houthis' attacks on ships in the Red Sea began in response to the conflict in Gaza, with the group claiming they were targeting ships linked to Israel.
Further incidents of drone attacks on ships in the Red Sea were reported on Saturday.
Lord Cameron said: “Iran has a thoroughly malign influence on the region and the world – there is no doubt about that.”
“There are the Houthis, there is Hezbollah, there are the Iranian-backed militias in Iraq who have actually attacked British and American bases and troops.”
“And of course Hamas.” So you have all these proxies, and I think it's incredibly important that Iran, first of all, gets an incredibly clear message that this escalation will not be tolerated.
“Second, we need to work with our allies to develop really strong deterrence measures against Iran, and it is important that we do that.”
“The level of danger and insecurity in the world is extremely high compared to previous years and decades, and the threat from Iran is part of that picture.”
The United Kingdom Maritime Trade Operations (UKMTO), a Royal Navy initiative that provides shipping operators with information about security incidents, flagged a series of attacks on Saturday.
There have been several reports of a drone flying low over a ship and then exploding about 1.5 nautical miles away. The incident occurred about 50 nautical miles off the Yemeni coast.
Another drone attack was reported in the Red Sea around 45 nautical miles from Saleef, Yemen.
Another incident occurred on Saturday about 200 miles southwest of Veraval in India – well beyond the Red Sea, which has been the focus of attacks on shipping. The US claimed a kamikaze drone launched by Iran hit a chemical tanker.
Lord Cameron's comments followed a visit to the Middle East during which he discussed the situation in the Red Sea with his Egyptian counterpart.
The Royal Navy warship HMS Diamond has already joined an international operation to protect cargo ships and Lord Cameron hinted at potentially greater British involvement in the coalition.
If the Red Sea is too dangerous for shipping, ships traveling between Asia and Europe will have to detour via the southern tip of Africa instead of using the Suez Canal, incurring additional costs.