The US military claims to have sunk six small Iranian boats as tensions continue to rise in the Strait of Hormuz.

US Central Command (Centcom) commander admiral Brad Cooper said Iran was targeting commercial shipping and US military ships with cruise missiles. An Iranian military official denied the US navy report, according to state television.

It comes after the United States rejected claims by Iran that two missiles struck an American warship intending to pass through the Strait of Hormuz on Monday.

Tehran’s semi-official state news agency Fars reported the warship was turned back after it was struck while sailing near Jask island, following an earlier threat from Iran to attack any US boats that sought to enter the strait.

Centcom said on X that “no US Navy ships have been struck”. It did not directly respond to claims that a warship had been made to turn back.

The United Arab Emirates, a key American ally, also said it had come under attack from Iran for the first time since the fragile ceasefire took hold in early April.

The UAE Defence Ministry said its air defences had engaged 15 missiles and four drones fired by Iran. Authorities in the eastern emirate of Fujairah said one drone sparked a fire at a key oil facility, wounding three Indian nationals. The UK Maritime Trade Organisation (UKMTO) reported two cargo vessels ablaze off the UAE.

The latest conflict came after US president Donald Trump had vowed to free commercial ships stranded in the waterway as part of his “Project Freedom”, an operation to guide foreign ships past Iran’s blockade, which was imposed shortly after the US-Israeli war on Iran began on 28 February.

Centcom later said that two US-flagged merchant vessels had passed through the Strait of Hormuz as US Navy guided-missile destroyers operated in the Gulf. Tehran has not yet responded to the claims.

Admiral Cooper claimed to establish a lane for ships to cross through the strait in Oman’s waters, saying it had set up an “enhanced security area.”

Trump warned Iran would be “blown off the face of the Earth” if they attack US vessels carrying out Project Freedom in an interview with Fox News’ Trey Yingst on Monday.

It came after his lengthy Truth Social post on Sunday, where he declared the “humanitarian” mission, beginning on Monday morning, would “free up people, companies, and Countries that have done absolutely nothing wrong”.

Several ships were running low on food and other supplies, he said.

“They are merely neutral and innocent bystanders! For the good of Iran, the Middle East, and the United States, we have told these Countries that we will guide their Ships safely out of these restricted Waterways, so that they can freely and ably get on with their business,” Mr Trump wrote.

He said “Project Freedom” came as the US held “very positive discussions” with Iran, who have reportedly issued the US president a one-month deadline for negotiations on its proposed deal to reopen the strait and bring an end to the war.

A senior Iranian lawmaker had previously warned that any US involvement in managing shipping through the Strait of Hormuz would constitute a violation of the ceasefire.

Ibrahim Azizi dismissed the idea that the waterway could be directed by Washington, saying the strait and the Persian Gulf “would not be managed by Trump’s delusional posts”.

“No one would believe Blame Game scenarios!” he added.

Hours before claiming to have struck a US warship, a statement from the Iranian military declared it would “respond harshly” to any threat from foreign vessels.

Ali Abdollahi, the head of the forces’ unified command, said in the statement that commercial ships and oil tankers must refrain from any movement in the absence of coordination with Iran’s military.

“We have repeatedly said the security of the Strait of Hormuz is in our hands and that the safe passage of vessels needs to be coordinated with the armed forces,” Mr Abdollahi said.

“We warn that any foreign armed forces, especially the aggressive US army, will be attacked if they intend to approach and enter the Strait of Hormuz.”

Later on Monday, US treasury secretary Scott Bessent called on China to step up efforts to help the US end Iran’s blockade of the waterway.

Washington will be watching to see whether China steps up its diplomacy with Iran, he added.