Finland considers web monitoring after shooting

"This type of networking was not possible before the internet era," said Aarne Kinnunen, a trained criminologist and adviser to Finland's justice minister.

"The internet creates the image that there is a crowd of people that respect this type of behaviour and ... misrepresentation of reality."

Videos linked to killing sprees gained widespread attention in 2007 when Cho Seung-Hui killed 33 people, including himself, at Virginia Tech university in the US and mailed a film explaining his actions to broadcaster NBC.

Analysts say web monitoring for malicious intent would be difficult since such threats were often vague, hoaxes commonplace and police resources limited. Kinnunen suggested linking internet background checks to new gun permits.

Google said in a statement the videos posted by the suspected gunmen on YouTube did not breach its "zero tolerance policy for threats and incitement to violence".