Investigators have concluded that an Iranian drone was used to bomb an oil tanker linked to an Israeli billionaire last week, the US navy said on Tuesday.

The drone attack on the Liberian-flagged oil tanker Pacific Zircon last Tuesday off the coast of Oman appears to be part of the long-running shadow war between Israel and Iran that has included the targeting of Israeli-linked ships in strategic Middle East waterways.

The navy said explosives experts boarded the ship to assess the damage, including a 30-inch hole punched in its side, and to collect debris and bomb residue.

The evidence was taken to a lab at the headquarters of the US Fifth Fleet in the Gulf Arab nation of Bahrain.

Navy investigators concluded that the drone used was an Iranian Shahed-136, the same kind of bomb-carrying drone Iran has supplied to Russia in its war on Ukraine.

Iranian drones were used by Yemeni rebels to attack Saudi Arabia and the United Arab Emirates earlier this year, the navy said.

“The Iranian attack on a commercial tanker transiting international waters was deliberate, flagrant and dangerous, endangering the lives of the ship’s crew and destabilising maritime security in the Middle East,” said vice admiral Brad Cooper, commander of US naval forces central command.

The Pacific Zircon is operated by Singapore-based Eastern Pacific Shipping, which is a company ultimately owned by Israeli billionaire Idan Ofer.

Israeli and US officials said at the time of the attack that they suspected Iran was behind it.

Iran has denied any involvement in the attack, with its mission to the United Nations dismissing the allegations as “false news” in a statement last week.

Last year a suspected Iranian drone strike hit the Israeli-associated oil tanker Mercer Street off Oman, killing two people on board.

In recent months, Iran has criticised its perceived enemies abroad amid months-long nationwide protests calling for the overthrow of its ruling clerics.