Seven alleged al-Qaeda members accused of planning attacks against British and American warships in the Gibraltar Straits are due to go on trial. They deny the charges.
The prosecution alleges that three Saudis, with the help of four Moroccans, planned to blow up Nato warships as well as attack buses in Morocco and a mosque in the centre of the city of Marrakech.
Morocco is also reported to be holding several other al-Qaeda suspects, including a man believed to be a senior member of the organisation.
The Saudi national, Abu Zubair - nicknamed "The Bear" for his huge frame - is suspected of planning attacks against Western interests in Morocco.
Another senior al-Qaeda agent, German citizen Mohammed Haydar Zammar, was also arrested by Moroccan authorities. He is believed to have been extradited to Syria.