http://www.islam-watch.org/Europe/Cu...-in-Europe.htm

While the phenomenon affects only a minority of European Muslims, its dimensions and repercussions are more than noteworthy. In London, city officials are worried about the growth of an extremely violent gang commonly known as the Muslim Boys. Operating in the southern areas of the British capital, the gang is composed of several hundreds of members and is active in criminal activities ranging from robberies to drug trafficking. The members of the gang are mostly British-born black youth originally from the Caribbean or Africa who converted to Islam in British penitentiaries and bond over their newfound faith (Evening Standard, February 3, 2005). Yet, their interpretation of Islam is perverted. The gang members do not respect the most basic tenets of Islam, and their appearance and slang more closely resemble that of American ghetto culture than that of practicing Muslims. Tellingly, a gang member admitted to a reporter from the Evening Standard: "I pray twice a day: before I do crime and after. I ask Allah for a blessing when I'm out on the streets. Afterwards, I apologize to Allah for what I done [sic]." The gang is also involved in "forced conversions," compelling black youth at gunpoint to convert to Islam and join them; two years ago, they executed a 24-year-old for refusing to convert.
Jihadism is a global movement whose characteristics mutate rapidly. While today some of the abovementioned trends are still in a developing phase or can be noticed only in some European countries, it is likely that they will be replicated with greater intensity and in more countries in the near future.
Numerous other sites point to indicators, but "hard" facts/evidence is hard to find.