WASHINGTON (AP) The U.S. Department of Transportation has concluded that a militant group linked to the al-Qaida terrorist network was responsible for an explosion on a Japanese tanker in the Strait of Hormuz in July and warned of further attacks.

In an advisory issued Friday, the department said, "Government and industry sources can confirm that the claim by the Abdullah Azzam Brigade that the group had attacked the tanker M. Star is valid."

On July 28, an explosion on the M. Star, owned and operated by Mitsui O.S.K. Lines Ltd., injured one of its crew members. The Abdullah Azzam group claimed responsibility for the blast and said the attack was carried out by a suicide bomber.

The U.S. advisory said, "The group remains active and can conduct further attacks on vessels in areas in the Strait of Hormuz, southern Arabian Gulf, and western Gulf of Oman."

It recommended that "all ships transiting the subject waters exercise increased vigilance and caution."