A Hamburg court on Wednesday sentenced to 15 years in prison -- the maximum under German laws -- Mounir al-Motassadek, the first man to stand trial over the 9/11 attacks.

The 28-year-old Moroccan, a student of electrical engineering, was found guilty of being an accessory to the murder of more than 3,000 people.

He was also convicted of being a member of a terrorist organisation, and of attempted murder and causing grievous bodily harm.

Motassadek was found to have helped a Hamburg-based terror cell as it plotted to hijack planes and fly them into the World Trade Centre and the Pentagon.

Defence lawyers said they would appeal against the conviction.

"The accused belonged to this group since its inception," said presiding Judge Albrecht Mentz. "He knew and approved the key elements of the planned attacks.

"This group of Arab-Muslim students planned the attacks out of hatred for the United States and Israel.

"They wanted to strike at the foundations of the United States with this attack of unprecedented dimensions."