Iran has repeatedly denied being involved in the June 13 attack on the Japanese tanker Kokuka Courageous and the Norwegian-owned Front Altair.
The comments by Cmdr. Sean Kido came as sailors showed reporters pieces of debris and a magnet the Navy says was used to attach an unexploded mine to the hull of the Kokuka Courageous. U.S. authorities say the materials were left behind by Iran's Revolutionary Guard when they spirited away the unexploded mine after the attack in the Gulf of Oman.
Iran, which has previously used mines against oil tankers in the crucial waterway in the 1980s, has also not acknowledged retrieving the mine.
Kido stressed that the damage to the Kokuka Courageous was "not consistent with an external flying object hitting the ship," as the ship's owner has contended happened during the attack.
"The damage we observed is consistent with a limpet mine attack," Kido said.
Meanwhile, rockets struck near an oil-drilling site in Iraq's southern Basra province early Wednesday, including one that hit inside a compound housing energy giant Exxon Mobil and other foreign oil companies and wounding three local workers, one seriously, Iraqi officials said.
The attacks come against the backdrop of heightened tensions between the U.S. and Iran following President Donald Trump's decision to withdraw from Tehran's nuclear deal with world powers a year ago.
Iran recently has quadrupled its production of low-enriched uranium and threatened to boost its enrichment closer to weapons-grade levels, trying to pressure Europe for new terms to the 2015 deal.
In recent weeks, the U.S. has sped an aircraft carrier to the Mideast and deployed additional troops to the tens of thousands already in the region. Mysterious attacks also have targeted oil tankers as Iranian-allied Houthi rebels launched bomb-laden drones into Saudi Arabia.
All this has raised fears that a miscalculation or further rise in tensions could push the U.S. and Iran into an open conflict, some 40 years after Tehran's Islamic Revolution.
The U.S. Navy briefed foreign journalists Wednesday at a 5th Fleet base near Fujairah, an Emirati port city some 210 kilometers (130 miles) northeast of the capital, Abu Dhabi. They showed journalists debris recovered from the Kokuka Courageous after the attack, including aluminum and composite metals.
They also displayed a magnet — one of six apparently used to attach the unexploded limpet mine to the ship's hull. Sailors said it took two of them and a crowbar to pry it off the ship.
Limpet mines take their name from a mollusk that clings to rock and have been used by a variety of militaries. The mines can be attached by both magnets and nails. The Kokuka Courageous also bore nail holes near where Iranian forces took the unexploded mine, the sailors said.
They showed reporters a photo of a limpet mine on display in Iran, which they said resembled the one used on the ship. The 90-pound (42-kilogram) conical-shaped mine had a sign next to it saying it was produced by a research company affiliated with the Revolutionary Guard, a paramilitary group that answers only to Supreme Leader Ayatollah Ali Khamenei.
"The limpet mine that was used does bear a striking resemblance to that which has been publicly displayed in Iranian military parades," Kido said. "There are distinguishing features."
Iran's mission to the U.N. declined to comment, referring reporters to remarks by Iranian Defense Minister Gen. Amir Hatami, who said allegations that Tehran was behind the tanker attacks was "totally a lie" meant to tarnish Iran's image.
According to the semi-official Fars news agency, Hatami questioned the authenticity of a grainy video released by the U.S. following the attack that purports to show Revolutionary Guard forces removing the unexploded mine.
"The date and the location shown in the footage have not been authenticated," he said. The Americans "can show any footage ... but it cannot be used as evidence."
The mines were placed above the vessel's water line. One exploded, punching through the double-hulled ship and sparking a brief fire. The mines' placement makes it "appear that the intention was not to sink the vessel," Kido said.
Authorities also recovered a handprint and fingerprints, he said. "We recovered biometric information ... which can be used to build a criminal case to hold the individuals responsible accountable." He did not offer more details.
The second vessel targeted in the attack, the Norwegian-owned Front Altair, caught fire and sent billowing black smoke into the air that was visible from space by satellites. Kido did not explain why the U.S. had no immediate evidence from that vessel. Both are now anchored off the eastern coast of the United Arab Emirates.
He also declined to discuss an earlier May 12 attack on four oil tankers off the coast of Fujairah, near the U.S. base. The U.S. has also blamed that attack on Iranian limpet mines.
Meanwhile, in Iraq on Wednesday, a Katyusha rocket landed at dawn near the Zubair and Rumeila oil fields operated by the Iraqi Drilling company, near a compound where Exxon Mobil and other companies house their workers, security official Mahdi Raykan said. Forty Exxon Mobil staffers were evacuated, Iraqi security officials said.
Exxon Mobil, based in Irving, Texas, did not respond to a request for comment. In May, it evacuated staff from the West Qurna 1 oil field in Basra province.
Iraq has worried about getting caught between the U.S. and Iran amid the rising tensions. The country hosts more than 5,000 U.S. troops, and is home to powerful Iranian-backed militias, some of whom want those U.S. forces to leave.
No one claimed responsibility for Wednesday's attacks and Iraqi oil exports were unaffected.
