Hundreds of al-Qaida documents have been discovered embedded inside a pornographic movie, including a plot to carry out an attack in Europe similar to the 2008 Mumbai attacks.

The documents were found after 22-year-old Austrian Maqsood Lodin was detained and searched by investigators in Berlin after flying from Pakistan via Budapest.

The investigators discovered a storage device and a memory card hidden in Lodin's underwear which contained a pornographic film called Kick Ass and a file marked Sexy Tanja.

Several weeks later, investigators decoded the device and found more than 100 al-Qaida documents embedded in the video, including terrorist training manuals and plans to seize cruise ships to launch an attack on Europe similar to the 2008 Mumbai attacks in which 10 gunmen killed 164 people.

US intelligence told CNN the materials discovered are the most important since the trove which were discovered during the killing of Osama Bin Laden last year.

One of the documents, entitled Future Works, was reported to appear to show discussions by al-Qaida to find new targets and methods of attacks. German investigators believe the document was written in 2009 and still forms a large part of al-Qaida's plans.

A year after the document was written; European intelligence agencies investigated a Mumbai-style plot involving Germany which sparked a US State Department travel warning for Americans in Europe.

Investigative journalist Yassin Musharbash, a reporter with theGerman newspaper Die Zeit, was the first to report on the documents. He was quoted as saying: "I think it is plausible to think that the 'Future Works' document is part of that particular project."

Musharbash told CNN: "The document delivers very clearly the notion that al Qaeda knows it is being followed very closely.

"It specifically says that Western intelligence agencies have become very good at spoiling attacks, that they have to come up with new ways and better plotting."

Lodin and alleged compatriot Yusuf Ocak, who was detained in Vienna two weeks later, was stopped in Berlin, are currently on trial in the German capital.

They have pleaded not guilty to terrorism charges. The men, who reportedly met in a terrorist training camp in Pakistan, were both listed on a watch list. Prosecutors said they believe the men were sent back to Germany to recruit others to take part in the attacks outlined in the documents.