By MARGARET COKER
—Spencer Swartz contributed to this article.
ABU DHABI— Investigators in the United Arab Emirates have concluded that an Omani suicide bomber in an explosives-laden motorboat attacked a Japanese-owned oil tanker last week as it traveled through the
strategically important Strait of Hormuz, according to a person familiar with the investigation.
The U.A.E., in a statement released Friday, became the first government to say that the mysterious incident on July 29, which dented the tanker's hull and slightly injured one of its crew, was a terrorist attack. An Emirati coast guard official confirmed that explosives caused the damage, according to the statement released by the U.A.E.'s state-run news agency.
Earlier this week, an al Qaeda-affiliated militant group believed to be based in Egypt claimed responsibility for the act, saying it had hoped to disrupt the global oil supply.
The owners of the tanker, the M. Star, have maintained that the boat was hit by an explosion, but officials in the region and in Washington had expressed skepticism about terrorist involvement, saying alternately that an unusually strong wave or collision might have damaged the vessel.
The person familiar with the investigation hadn't yet concluded whether the militant group's claim of responsibility was correct. But, forensic evidence collected on the ship, including traces of explosives, and details collected by intelligence services in the region left no doubt about the nature of the attack, the person said.
"It was a very amateurish attempt, but it was clearly a failed terrorist attack," the person said. The bombing is thought to be the first time that Islamic extremists have targeted oil shipments in the strategic waterway, a shipping route from the Persian Gulf through which 20% of the world's global oil supply travels each day.
A spokesman for the U.S. Navy's Fifth Fleet, which is based in Bahrain and patrols the Strait, said in a statement that it was aware of the reports of explosive residue found on the tanker and that Navy experts were in contact with Emirati officials to discuss the findings.
Spokesman Lt. John Fage said the Navy had no plans to change its normally high state of vigilance in the Strait of Hormuz.
A spokeswoman for Japan's Ministry of Foreign Affairs said the government is still investigating the cause of the damage to the ship. A spokeswoman for Mitsui O.S.K. Ltd., the Japanese company that owns the tanker, had no comment.
The U.A.E. led a weeklong probe of the July 28 incident, with help from the U.S. Navy and the Oman and Japanese governments, after the tanker had docked in its Port of Fujairah. The U.A.E. is leading the investigation, with help from the U.S. Navy, and the Oman and Japanese governments.
The M. Star on Friday left the port to continue its journey to Japan, according to the Emirati coast guard, the U.A.E. state-run news agency reported.
Shipping and oil industry analysts took the latest announcement with relative equanimity, saying they wanted to see more detailed evidence to confirm last week's incident as a terrorist attack.
"Apart from the pictorial evidence of damage to the vessel, there is no corroborated information for insurers to work with," said Neil Roberts, a senior executive of underwriting at Lloyd's Market Association.
Oil markets, focused Friday on weak U.S. jobs data and the implications for weaker crude demand, shrugged off the U.A.E. government's conclusion. "While this highlights security concerns at the world’s most important oil supply choke point, the scale of the attack seems pretty low-brow," JP Morgan said Friday in a research note.
One shipping industry source said insurance premiums for tanker operators could soar if they're forced to insure against the threat of terrorist attacks against crew, vessels and cargo. The shipping industry is already paying higher insurance coverage because of an increase in Somali pirate attacks on cargo vessels over the past couple of years.
In a statement posted on a militant website and dated Aug. 2, the Abdullah Azzam Brigades, a militant group named after one of Osama Bin Laden's religious mentors, claimed responsibility for the attack. The group identified the bomber as Ayyub Al Tayshan, and said he blew himself up in the Strait of Hormuz between the U.A.E. and Oman.
The statement didn't give any precise details about how the group attacked the vessel, or selected that specific ship. However, it said that the group deliberately chose the location of the attack, saying it wanted to "weaken the global infidel order that has assumed authority over Muslim lands, looting their resources, and to lift the oppression of Muslims."
The person close to the investigation said intelligence services in the region have identified the bomber as a young Omani man from a coastal village north of the capital, Muscat. The person said he wasn't authorized to release the bomber's name.
Intelligence agencies in the region have determined that the Omani was in contact with terrorist elements in the wider Middle East for the past two months, but they haven't conclusively linked him to the Abdullah Azzam Brigades, the person said.
Local intelligence officials don't believe that the bomber had received any formal military or explosives training, the person said. Forensics evidence from the hull of the tanker showed that the explosives used were a homemade compound employing TNT-like materiel, the person said.
"The bomb he made was homemade and very weak," the person said. The agencies are still investigating how the bomber was radicalized and the extent of his links with global jihadist organizations, the person said.
For the past week, Omani intelligence officials have been conducting sweeps along their coast searching for evidence of a wider terrorist network there, according to the person. It is unclear whether the surveillance has yielded any arrests.
The Abdullah Azzam Brigades has claimed responsibility for multiple previous terrorist attacks. Between 2004 and 2005 the group said it carried out a string of bombings at Sharm el-Sheikh and along the Sinai Peninsula that killed more than 100 people. Egyptian courts convicted four militants, calling them homegrown radicals that weren't affiliated with al Qaeda.
In a separate attack in 2005, the group claimed it had fired rockets from Egypt's Sinai Peninsula at two U.S. naval vessels docked in the nearby Aqaba port in Jordan—though other militant groups also claimed responsibility.