An American-guided missile destroyer was sent to assist two burning tankers in the Gulf of Oman, following what the Trump administration on Thursday described as a "blatant assault" by Iran.
Following the attack that could further inflame tensions between Washington and Tehran, the USS Bainbridge was dispatched to help the damaged Japanese and Norwegian vessels, according to 5th Fleet spokesman Cmdr. Josh Frey.
Secretary of State Mike Pompeo said the weapons used and previous threats issued by Iran point to Tehran as the culprit.
"It is the assessment of the United States government that the Islamic Republic of Iran is responsible for the attacks that occurred in the Gulf of Oman today," he said.
"This assessment is based on intelligence, the weapons used, the level of expertise needed to execute the operation, recent similar Iranian attacks on shipping and the fact that no proxy group operating in the area has the resources and proficiency to act with such a high degree of sophistication," said Pompeo, who didn't offer further evidence.
"Taken as a whole these unprovoked attacks present a clear threat to international peace and security, a blatant assault on the freedom of navigation and an unacceptable campaign of escalating tension by Iran.
Thursday evening, U.S. Central Command described the incident as a limpet mine attack. A limpet mine is a naval mine attached to a target with magnets.
Central Command released video it said showed an Iranian Revolutionary Guard Corps patrol boat approaching one of the ships, the Kokuka Courageous, hours after the explosion and “and was observed and recorded removing the unexploded limpet mine from the M/T Kokuka Courageous.”
Central Command spokesman Capt. Bill Urban said the crew of the Kokuka Courageous abandoned their ship after discovering a probable unexploded limpet mine on its hull following an initial explosion.
The U.S. military also said that a U.S. aircraft observed a Revolutionary Guard Corps patrol boat and multiple fast attack craft in the vicinity of the other ship that was damaged, the Altair, after the distress calls.
American vessels were "rendering assistance" following the reported attack, the U.S. 5th Fleet said in a earlier statement.
The owner of one of the tankers, the 560-foot tanker Kokuka Courageous, said that vessel had been struck by a projectile that pierced its hull and started a fire.
"We received word that our ship was attacked," Yutaka Katada, president of Japan's Kokuka Sangyo shipping company, told a news conference.
All 21 of its crew members were forced to abandon ship and were picked up by a nearby Dutch-flagged tugboat, Bernhard Schulte Ship management said in a statement.
One person suffered minor injuries, but the ship's cargo of methanol was intact and the Kokuka Courageous was not in danger of sinking, according to vessel's management firm.
Thursday's incident came as Japanese Prime Minister Shinzo Abe was wrapping up a two-day trip to Iran on a mission to improve relations between Washington and Tehran.
"While I very much appreciate P.M. Abe going to Iran to meet with Ayatollah Ali Khamenei, I personally feel that it is too soon to even think about making a deal," President Donald Trump tweeted. "They are not ready, and neither are we!"
Noting that Abe's visit coincided with attacks on "Japan-related tankers," Iranian Foreign Minister Javad Zarif tweeted that "suspicious doesn't begin to describe what likely transpired this morning."
The other ship, the 800-foot Norwegian-owned Front Altair, was damaged by an explosion and a fire, that vessel's management company said.
The ship was carrying a cargo of naphtha, a flammable liquid hydrocarbon, International Tanker Management said in a statement.
All 23 crew members on the Front Altair were "safe and accounted for" after being picked up by another nearby tanker, according to Martin Baxendale, who was speaking on behalf of the firm.
"We're trying to establish what's happened on board," Baxendadale added. "We would all do well to wait for the details before jumping to conclusions."
Urban, the Central Command spokesman, said in Thursday evening’s statement the U.S. and the international community "stand ready to defend our interests, including the freedom of navigation.”
“The United States has no interest in engaging in a new conflict in the Middle East. However, we will defend our interests,” Urban said.
Oil prices jumped as much as 4 percent following Thursday's incident.
Coordinates given by the United Kingdom Maritime Trade Operations, which is run by the British navy, as well as the ship tracking website Marine Traffic, said the damaged vessels were both within 30 miles of the Iranian coast.
Last month, four oil tankers from Saudi Arabia, the UAE and Norway were damaged in the Gulf of Oman. All three countries said it was the work of a "state actor." They said it was likely the work of sophisticated and coordinated teams, deploying trained divers armed with magnetic limpet mines that were attached to the ships' hulls.
Saudi Arabia and the U.S. blamed Iran, an allegation it denied.
The top commander of U.S. forces in the Middle East last week said that "the threat is imminent" of an attack by Iran or its proxies. The Trump administration had previously announced additional troops, an aircraft carrier strike group, Air Force bombers and Patriot missiles being sent to the region.
Trump has also withdrawn from 2015's landmark Iran nuclear agreement, has imposed sanctions that squeezed the country's economy and designated its powerful Revolutionary Guard Corps as a foreign terrorist organization.
Iran denies claims that it wants to attack U.S. forces, with its ambassador to the United Nations telling NBC News in May that the rhetoric coming from Washington was dangerous and mirrored the run-up to the Iraq War.
Ambassador Majid Takht Ravanchi called such statements "fake intelligence."
However, Thursday's incident follows recent comments from Trump and Secretary of State Mike Pompeo that they would be willing to enter into talks with Tehran.
And earlier this week Iran released U.S. resident Nizar Zakka, who had been imprisoned in the Islamic Republic for four years.
Alexander Smith, Caroline Radnofsky and Linda Givetash reported from London, Kurt Chirbas and David K. Li from New York, Courtney Kube, Abigail Williams and Moshe Gains from Washington and Arata Yamamoto from Tokyo.