Social media websites such as Twitter and Facebook play a crucial role in recruiting foreign fighters to travel to Syria, the European Union's anti-terror chief has warned.
Gilles de Kerchove told MPs that online messages, many posted by "narcissistic" youths posing with AK-47 rifles, had contributed to an acceleration in the number of Europeans, including Britons, travelling to Syria to fight - with many falling in with extremist groups.
He said talks had begun with internet giants to find ways to remove illegal and "undesirable" websites, photos and videos encouraging would-be jihadists.
Giving evidence to the Home Affairs Select Committee - which heard that up to 11,000 foreign fighters are in Syria - the EU's counter-terrorism co-ordinator said one of the reasons was that it was "so easy" for Europeans to get to compared to other conflict zones.
Syria's environment was another factor, he said: "Many of the would-be jihadists are urban people. The environment is more similar in Syria than it is in the desert."
But he added the "internet, social media - Facebook, Twitter - plays a huge role in this acceleration".
He said: "A lot of these young jihadists are narcissists. They want to be portrayed with a Kalashnikov, they put themselves, their pictures, on YouTube, on Facebook. They try to encourage colleagues, friends to join."
He said the internet was a "critical recruiting factor" and the social media sites "play a significant role in indoctrination, recruitment, radicalisation".
Mr de Kerchove also said satellite TV allowed viewers to watch channels where "you have preachers calling for violent jihad".
Setting out the action being taken by the EU he said: "The Commissioner for Home Affairs will set up a forum to discuss with the big players - Google, Facebook, Twitter - how we can improve the way one removes from the internet the illegal and if not illegal, undesirable websites.
"But it is very sensitive because it raises the question of the balance with freedom of speech. So how can we improve referral mechanisms by which the users themselves let Google know that they find some unacceptable websites and videos and pictures on the internet?
"This is a discussion that we have started with these big companies."