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, wounding three Indian nationals. 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.

Adm. Brad Cooper, commander of U.S. Central Command, told reporters that American forces have opened a passage through the strait and that U.S. military helicopters have sunk six Iranian small boats that were targeting civilian vessels.

He said Iran has launched multiple cruise missiles, drones and small boats at ships the U.S. military is protecting, and that “each and every one” of the threats had been defeated.

Breaking Iran’s chokehold on the strait would ease global economic concerns and deny Tehran a major source of leverage. But such efforts also risk reigniting the full-scale fighting that erupted when the U.S. and Israel first attacked Iran on Feb. 28, prompting it to close the strait.

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 had advised ships Monday to cross the strait in Oman’s waters, saying it had set up an “enhanced security area.”

Reports of new attacks raised doubts as to whether shipping companies, and their insurers, would take such a 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 Arabian 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 Arabian Gulf since the war began.