Moroccan officials say three suspected al-Qaida followers arrested last month were planning attacks against U.S. and British warships.
The officials say the attacks were being planned in the Strait of Gilbraltar.
The officials say the three men who are being held in custody in Casablanca are Saudi nationals.
The information was given late Monday.
In October 2000 in Yemen, a suicide boat attack blamed by the United States on Osama bin Laden's al-Qaida network killed 17 U.S. sailors.
Meanwhile, authorities in Tunisia are looking into whether al-Qaida was behind an attack on a synagogue in the resort town of Djerba in April that killed 19 people, most of them German.