A group of Al Qaeda terrorists, including two of the pilots who flew into the World Trade Center, met in Amsterdam in 1999, a German security official said Friday.

The official, who spoke on condition of anonymity, said Al Qaeda members met twice in the Netherlands while attending "Islamic seminars."

The meeting in mid-June 1999 was attended by pilots Mohamed Atta and Marwan al-Shehhi, and Ramzi Binalshibh -- the man who this week claimed on Arabic satellite network Al-Jazeera to have coordinated the Sept. 11 attacks. Mounir El Motassadeq, the only person under arrest in Germany for direct involvement in the Sept. 11 attacks, was also present.

The Dutch Internal Security Service declined to comment, and Dutch prosecutors investigating other Al Qaeda operations in the Netherlands said they were unaware of the meeting.

German prosecutors, however, had confirmed that at least one member of the Hamburg Al Qaeda cell visited the country.

At a news conference Aug. 29, German prosecutor Kay Nehm said El Motassadeq embraced Islamic fundamentalism after visiting the Netherlands.

Nehm said the first seminar was held in Eindhoven in early 1999, the second in Amsterdam in mid-1999 -- apparently the same seminar where, according to the source, they met with Binalshibh.

Dutch daily newspaper De Telegraaf reported Friday that the group used a conference on "Muslim Puritanism" held at an unidentified Amsterdam mosque as a cover for their meeting.

A second Dutch paper, the Eindhoven Dagblad, reported Thursday that El Motassadeq also visited Eindhoven in the fall of 1999 and again in 2001. Both papers cited unidentified members of the Internal Security Service.

The German source couldn't confirm either paper's report.

Fourteen alleged terrorists have been arrested in the Netherlands since Sept. 11, 2001, and are awaiting trial.