They contained copies of videos, songs, speeches and images that followers are encouraged to pass on.

Some were using Bluetooth short-range radio technology to anonymously spread information to potential supporters.

The study was led by German researcher Nico Prucha who has spent seven years cataloguing the materials put online by Jihadists.

Mr Prucha said that without technologies such as the web and mobile phones, al-Qaeda may well have withered a long time ago.

"It's the only way for them to remain part of the debate," he said. "Without it they would be isolated like they were in the 1980s."

Mr Prucha said that before the rise of the internet it was difficult for those interested in al-Qaeda or other militant groups to find information.

Often, he said, it came down to a chain of personal connections that led to someone directly involved in one of the active cells of the group.

Propaganda materials produced by these cells did manage to reach some followers by being copied again and again as they were passed around. However, the endless copying limited their effectiveness, especially when it came to videos.

"If you copy a VHS tape 10 times the quality gets really bad," said Mr Prucha, adding that the web had removed these limitations.

"Now I don't need to know any jihadists to see these materials," he said. "And the quality does not degrade over time."

The study by Mr Prucha and security consultant Nigel Stanley suggested that Jihadist efforts to reach people seeking information about the Islamic faith is extending to mobiles and smartphones.

Some militant groups have established wings or brigades that specifically prepare material for smartphones and brand their productions with their logo as a guarantee of authenticity.

Included in the packages of material studied by the researchers were copies of the Koran, audio readings, songs, speeches by Osama Bin-Laden, photoshopped pictures of the 9/11 attacks and videos shot by Jihadist fighters during military campaigns.

Much of the material appeared to be professionally produced, said Mr Stanley.

"It's not the rubbish you might get from someone in a back bedroom" said Mr Stanley. "It's been thought about, considered and has high production values."

The material is formatted for viewing on mobiles and for the particular mobile operating systems found in Arab nations.

Mobiles had become popular with militant Islamists as a propaganda spreading tool because they were "intimate" devices and rarely shared, said Mr Stanley.

They had also assumed particular importance in many Arabic nations where contact between the sexes is limited. In such situations, many people leave their Bluetooth connection turned on so they can make contact with members of the opposite sex without breaking local or religious customs.

Jihadists were exploiting this tendency to leave Bluetooth on and using the technology to anonymously distribute the propaganda packages, said Mr Stanley.

To have any lasting influence, knowledge about how militants spread their messages must go beyond the academic community and places such as Jihadica that document the online efforts of militant Islamists, said Mr Prucha.

"We need to understand their appeal and their calls to radicalise," he said. "But if we keep that information to ourselves without sharing it with Muslim communities there's no greater good coming out of it."