DUBAI, United Arab Emirates (AP) — The United Arab Emirates said Monday it came under attack by Iran for the first time since a fragile ceasefire took hold in early April. The attacks appeared to be in response to U.S. President Donald Trump’s latest efforts to reopen the Strait of Hormuz, a critical waterway for global energy.

The UAE Defense Ministry said Iran had launched four cruise missiles, with three shot down and one falling into the sea. Authorities in the eastern emirate of Fujairah said an Iranian drone sparked a fire at a key oil facility. The British military reported two cargo vessels ablaze off the UAE.

The attacks came after the U.S. military said two American-flagged merchant ships had successfully transited the Strait of Hormuz after it launched a new initiative to restore traffic Monday.

Iran has effectively controlled the strait since the U.S. and Israel launched the war in late February. Breaking Iran’s chokehold would ease global economic concerns and deny Tehran a major source of leverage in talks aimed at ending the war. But such efforts also risk reigniting full-scale fighting.

The South Korean government said an explosion and fire had broken out aboard a South Korean-operated ship anchored in the strait off the UAE. No injuries were reported. It was not immediately known if the vessel was one of the burning ships reported by the British military’s United Kingdom Maritime Trade Operations center.

Iran's effective closure of the strait, which runs between Iran and Oman, has caused a spike in worldwide fuel prices and rattled the global economy. The U.S.-led Joint Maritime Information Center is now advising ships to cross the strait in Oman’s waters, saying it set up an “enhanced security area.”

Reports of new attacks raised doubts as to whether shipping companies, and their insurers, will feel comfortable taking the risk given that Iran has fired on ships in the waterway and vowed to keep doing so. Iran has said the new U.S. effort is a violation of the fragile ceasefire that has held for more than three weeks.

Trump warns of ‘forceful’ response if Iran interferes

The U.S. military’s Central Command said the two American-flagged merchant ships were “safely headed on their journey” after transiting the Strait of Hormuz. It said Navy guided-missile destroyers in the Persian Gulf were helping to restore traffic.

Its statement on X said that U.S. destroyers had also transited the strait. It did not say when the Navy ships arrived or when the merchant vessels departed.

Trump's announcement Sunday that the U.S. would “guide” ships out of the strait warned that Iranian efforts to block them “will, unfortunately, have to be dealt with forcefully.”

He described “Project Freedom” in humanitarian terms, designed to aid stranded seafarers on hundreds of ships that have been stuck in the Persian Gulf since the war began. Crews have described to The Associated Press seeing drones and missiles explode over the waters earlier in the war as their vessels run low on drinking water, food and other supplies.

Iran’s state-run IRNA news agency called the effort part of Trump's “delirium.”

Iran stands firm on its grip of the strait

Iran’s military command on Monday said ships passing through the strait must coordinate with them.

“We warn that any foreign military force — especially the aggressive U.S. military — that intends to approach or enter the Strait of Hormuz will be targeted,” Maj. Gen. Ali Abdollahi told state broadcaster IRIB.

The extent of the attack on Fujairah was unclear, but it is the terminus of a pipeline the UAE has used to avoid shipping some of its oil through the strait. The emirate on the Gulf of Oman is home to extensive oil storage facilities and is the UAE’s main sea access outside the strait.

The disruption of the waterway has squeezed countries in Europe and Asia that depend on Persian Gulf oil and gas, raising prices far beyond the region.

The U.S. has warned shipping companies they could face sanctions for paying Iran for transit of the strait.

The Joint Maritime Information Center urged mariners to coordinate closely with authorities in Oman “due to anticipated high traffic volume.” It warned that passing close to usual routes “should be considered extremely hazardous due to the presence of mines that have not been fully surveyed and mitigated.”

The head of security for the Baltic and International Maritime Council, a leading shipping trade group, said no formal guidance or details about the U.S. effort had been issued to the industry. Jakob Larsen questioned whether the effort was sustainable and said it carries a “risk of hostilities breaking out again.”

The United Arab Emirates accused Iran of targeting a tanker linked to its main oil company with two drones as it navigated the strait. It did not say when the attack occurred. No injuries were reported.

U.S. military denies that Iran struck one of its ships

Iranian news agencies, including the semiofficial Fars and ILNA, reported Monday that Iran struck a U.S. vessel near an Iranian port southeast of the strait, accusing it of “violating maritime security and navigation norms.” The reports said the vessel was forced to turn back.

U.S. Central Command said on X that “no U.S. Navy ships have been struck.”

The U.S. has enforced a naval blockade on Iranian ports since April 13, telling at least 49 commercial ships to turn back, according to Central Command.

The blockade has deprived Tehran of oil revenue it needs to shore up its ailing economy. U.S. officials have expressed hope that the blockade forces Iran to make concessions in talks on its disputed nuclear program and other longstanding issues.

Little progress seen in negotiations

Iran’s latest proposal for ending the war calls for the U.S. lifting sanctions, ending the blockade, withdrawing forces from the region and ceasing all hostilities, including Israel’s operations in Lebanon, according to the semiofficial Nour News and Tasnim agencies, which have close ties to Iran’s security apparatus.

Iranian officials said they were reviewing the U.S. response, though Foreign Ministry spokesperson Esmail Baghaei told reporters Monday that changing demands made diplomacy difficult. He did not give details.

Iran has claimed its proposal does not include issues related to its nuclear program and enriched uranium — long a driving force in tensions with the U.S. and Israel.

Iran wants other issues resolved within 30 days and aims to end the war rather than extend the ceasefire. Trump expressed doubt over the weekend that the proposal would lead to a deal.

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Metz reported from Ramallah, West Bank. Associated Press journalists Munir Ahmed in Islamabad, Pakistan; Tong-hyung Kim in Seoul, South Korea; and Russ Bynum in Savannah, Georgia, contributed.