A wave of biker gangs from the US, Canada and Australia arriving in Europe has raised fears of deadly turf battle like the Nordic biker wars of the 1990s, European police agency Europol warned on Friday.
Gangs such as the Comancheros and Rebels from Australia, Rock Machine from Canada and the Mongols and Vagos from the US were moving into Europe, said a Europol statement.
The total number of what it called Outlaw Motorcycle Gangs (OMCG) in Europe now ran at more than 700, it said.
The gangs were seeking out particularly a dangerous hard core of recruits in their bid to seize territory to traffic drugs, weapons and people.
Now they were approaching far-right militants, prison gang members, hooligans and military personnel to exploit their expert knowledge, said Europol.
"Merely establishing a chapter on the 'turf' of another OMCG is interpreted as an act of provocation and is likely to result in violent confrontations and retaliation," the agency said.
The gangs "have a propensity to use extreme forms of violence", including with Kalashnikov assault rifles and grenades.
Modern biker gangs were becoming less associated with the biker lifestyle, with some members having neither a motorbike nor a driving licence, Europol noted.
Biker gangs were also involved in territorial disputes with local organised crime groups and street gangs, it added.
Europol said it had informed national police forces of the risk of clashes "and the possible impact on the general organised crime situation".
Europol said the so-called 'Nordic Biker Wars' of the 1990s were "a compelling example of the capacity for extreme violence resulting from an increased concentration of OMCGs in Europe."
The deadly conflict exploded when the Bandidos gang penetrated Nordic countries and challenged the Hell's Angels for a region that had been under their control for more than a decade.
Bikers used weapons including assault rifles, anti-tank weapons and car bombs against each other, leaving at least 11 bikers dead and dozens wounded.