A prominent Jewish group has said that web "hate sites", which feature advertisements for suicide bombers and violent shoot 'em up games, have increased dramatically since 11 September.

Rabbi Abraham Cooper, of the Los Angeles-based Simon Wiesenthal Centre, told Reuters that, according to its research, "extremist groups are undoubtedly spending more of their efforts online".

Rabbi Cooper explained that researchers had investigated over 25,000 sites, deeming 3,300 as "problematic", up from 2,600 last year.

"The biggest difference now is that we're seeing more websites enlisting suicide bombers and those that validate or encourage terrorism, and more games targeting minorities," he said.

The offending online games include Kaboom!, in which players act as a suicide bomber searching for crowds to cause as much bloodshed as possible.

Another game, NZ Manager from Austria, is said to let players manage a concentration camp filled with Turkish immigrants.

Other websites cited by Rabbi Cooper feature white supremacist games from the US and Sweden.

He said that the sites appealed to "leaderless resistance or the lone wolf".