Extremists who try to radicalise young people should be treated like those who groom children for abuse, an MP has said.
Cardiff South and Penarth MP Stephen Doughty called for action over the behaviour which he described as "very twisted".
Meanwhile, pictures obtained by The Wales Report show a man holding an Islamic State poster in Cardiff city centre in July.
Leaflets were also distributed.
"There is a low level entryism by some of the more extreme organisations," Mr Doughty said.
"They attempt to have very low level, open conversations with young people about their religious faith, concerns and international events in a very twisted and duplicitous way.
"They get that open conversation going and next time invite young people to a conference somewhere else in the UK.
"That's where the real radicalisation I believe is actually happening."'Heinous acts'
Last year two young men from Cardiff, Nasser Muthana and Reyaad Khan went to fight for Islamic State (IS) in Syria.
A friend of Mr Muthana said earlier this week he is worried about a presence of IS members in Cardiff.
Mr Muthana's younger brother Aseel Muthana, 17, is also believed to be in Syria, among an estimated 500 hundred UK nationals.
"We need to be looking very carefully at those who are coming into this community, those who are using the internet and social media to target young people," Mr Doughty added.
"This is the same as child abusers, those who groom people for other heinous acts and we need to look at that in the same way.
"This isn't someone deciding to go out and fight tomorrow, this is a process that takes place over many many months and we need to be getting to the root causes, and tackling those who are coming in to do this in our community."
In the Butetown area of Cardiff, youth group "Movement for Change" is working in the community to try to combat the threat of extremism.
But group leader Stewart Owadally said young people do not have enough confidence or trust in the police to report any instances of radicalisation.
"That's a massive problem," he said. "The young people tend to know what is going on.
"They know who their friends are, who are at risk. At an early stage if they had that confidence to go to the police, it would all change."
South Wales Police and Crime Commissioner Alun Michael said police are doing all they can to work with the community.
"The relationship between the police and young people is far more effective, and focused on winning the confidence of young people, that I've ever seen in the past," he told the programme.