LONDON (Reuters) - Ships should adopt heightened vigilance when transiting the Strait of Hormuz after a Japanese tanker was damaged in the waterway and indications point to a possible attack, the ship's flag registry said on Wednesday.
The 333-meter M.Star tanker, owned by Japan's Mitsui O.S.K. Lines Ltd. and registered in the Marshall Islands, was damaged last month by a mystery explosion while traveling near to the Strait, which handles 40 percent of the world's seaborne oil.
The Marshall Islands, which is the world's third-largest open ship registry, issued an advisory this week urging ships to "exercise the highest level of vigilance and caution, particularly during night transits with increased monitoring of small vessel and boat activity".
"We cannot positively confirm that it was a terrorist attack at this time, but the indications would imply that that might be what took place," Thomas Heinan, Deputy Commissioner of Maritime Affairs with the Republic of the Marshall Islands, told Reuters on Wednesday.
"And as a result we needed to advise ship owners and operators what to watch out for and what to do if a ship finds itself in a similar situation," he said in an interview.
A militant group called Abdullah Azzam Brigades, which is linked to al Qaeda, said that a suicide bomber belonging to it had attacked the tanker.
"Although the incident is still under investigation, it can be said that the very suspicious activity of two small craft observed on the vessel's radar and recorded by the ship's voyage data recorder and subsequent forensics tend toward supporting the belief that an unsuccessful terrorist bombing attempt was made on the M. Star," the Marshall Island's advisory said.
Some security analysts were skeptical of the group's claim, though the United Arab Emirates state news agency said investigators had found traces of explosives on the tanker.
This is the first advisory issued for the Strait of Hormuz by the Marshall Islands, which has sent investigators as part of the team probing the cause of damage to the M.Star.
"Given the current investigation we felt compelled to provide additional guidance to ship owners and operators should they find themselves in a situation where there might be similar activities or incidences taking place," Heinan said.
The U.S. Department of Transportation's Maritime Administration issued a similar advisory to vessels last week urging increased caution around Hormuz.
One crew member was injured in the M.Star incident. There was no oil spill or disruption to shipping.
Japan's Transport Ministry said on Wednesday checks had found a soot-like substance in a large dent in the tanker's hull but it was unclear what caused the blackish substance and it was being analyzed further.
"Our investigation is not yet complete and we have not received any official findings from any other participating governments," Heinan said.
He said it had not been able "to glean any definitive timeline" on how long the investigation would last.
There have been growing concerns for maritime security in the area. Al Qaeda has threatened to attack shipping there in the past.
Al Qaeda bombed the USS Cole warship in October 2000 when it was docked in the southern Yemen port of Aden, killing 17 U.S. sailors. Two years later an al Qaeda attack damaged a French tanker in the Gulf of Aden.
Editing by Alison Birrane