They beat up black and Arab football fans, terrorize immigrant neighborhoods, smash Muslim and Jewish gravestones, preach hate and rally support online. Norway's attacks laid bare a fringe of flourishing racist anger around Europe _ and exposed the risk that it could erupt into violence anywhere, anytime.
In interviews and online forums, European far-right extremists have not softened their rhetoric since Norway's massacre left 77 dead. They may recoil at the attacker's methods, but not his message: that Muslim immigrants are a threat to European survival.
"If there were no immigrants, there would never have been this drama," one French blogger says. Jean-Marie Le Pen, France's firebrand icon of anti-immigrant politics, said Norway "did not estimate the global danger that massive immigration represents, which is the principal cause" of the attacks.
The rise of anti-immigrant thought in the European political mainstream may even be increasing the risk. As far-right parties such as Le Pen's National Front have become more moderate and appealing to a broader spectrum of voters, they have jettisoned their most extreme members _ creating rage at the farthest fringes.
"These most extreme members are then left alone without the moderating influence of their former party colleagues," said Marko Papic of U.S.-based analyst group Stratfor.
In Internet chatter, some of the most extreme European voices even say Anders Behring Breivik wasn't xenophobic enough. Spain's Democracia Nacional, Russia's Slavic Union and the Swedish Resistance Movement dismissed him as a Zionist.
Europe's right-wing extremists are exceptional voices, numbering in the thousands. But their voices can take on disproportionate weight and skew perceptions of immigration.
Foreign-born people made up 9.4 percent of the population of the 27 European Union states last year, or 47 million of the EU's half a billion citizens, according to statistics agency Eurostat. But millions of those "foreigners" originally came from another EU country.
The proportion of the foreign-born is low compared to the United States, but has been rising steadily and is unsettling to some in Europe, where many countries were relatively homogenous until recent generations.
As xenophobic sentiment bleeds into the mainstream, authorities are closely watching the activities of the hardened extremists.
The French police unit monitoring extremist activity online registered more than 8,000 complaints last year of racist or xenophobic commentary. Police determined just 10 serious potential threats, according to an official with the Central Office of Judicial Police. The official was not authorized to be publicly named because of the sensitivity of his job.
While most European extremists active online sought to distance themselves from Breivik, Russian neo-Nazis and far-right Russian nationalists hailed his killing spree _ and hinted of similar attacks in Russia.
"The white race is attacking: The White Hero of Norway Anders Bering Breivik," read the headline on the website of the Slavic Union, one of Russia's largest neo-Nazi groups.
"The more legal nationalist organizations are destroyed, the more Breiviks there will be," Dmitry Demushkin, former leader of Slavic Union who now heads the Russkie _ or Russians _ nationalist movement, told The Associated Press.
Russia's leadership has long been accused of allowing nationalist gangs to operate with impunity. But even in western Europe, where governments are more sensitive to public opinion, there were pockets of far-right support for Breivik's rhetoric.
The leader of the English Defense League, a British far-right group to which Breivik claimed links, said the desperation among those angry at immigration is a "ticking time bomb."
France's National Front suspended a member whose blog praised Breivik as an "icon," and Italy's Northern League suspended a member who called some of the gunman's ideas "great."
Breivik's actions also drew continent-wide attention to far-right causes.
Yannick Cahuzac of the University of Perpignan, who analyzes far-right activity online, said one of France's most widely viewed extreme right sites, Fdesouche.com, has seen a rise in visitors since the Norway massacre.
It's difficult to discern whether the ranks of right-wing extremists in Europe are growing, in part because many are isolated figures who haven't declared public allegiance to a single party or cause.
Sweden's Brottsforebyggande Radet, the national crime-prevention agency, reports a 10 percent drop in xenophobia-motivated crimes between 2008 and 2011. At the same time, far-right activity online in Sweden, and elsewhere, has soared.
In Germany, far-right groups ran some 1,000 websites and 38 online radio stations as of late last year.
Cahuzac says the aggressive rhetoric online may not be a bad thing. "It can be cathartic, as you sublimate your violence via words," he said. "It's a diversion, an outlet for this hate that cannot always be expressed in public."
In Serbia, for example, a nationalist group gathered over 70,000 "likes" in support of Moammer Gadhafi on Facebook at the start of the NATO intervention in Libya. But when they tried to organize street protest in Belgrade against the Western intervention, only a few hundred people showed up.
The radicals, while small in number, can at times pose a real danger.
In Russia, neo-Nazis have been convicted of killing and assaulting dark-skinned non-Slavs, and Muslim labor migrants from the Caucasus and Central Asia are regularly targeted for attack.
On Paris' famed Champs-Elysees, a radical right-wing militant shot at then-French President Jacques Chirac in 200. More common but less eye-catching is vandalism. This week, swastikas and Nazi symbols were scrawled on a church in western France.
In Greece, the gateway for masses of Europe's illegal immigrants, hundreds of black-shirted, bat-wielding youths chased down immigrants through the streets of Athens and knifed and beat them in May.
Since Norway's attacks, Greek police have stepped up patrols in neighborhoods with high ethnic tensions, and some British mosques stepped up security.
In Poland, which is struggling to stem hooliganism before it hosts the European football championships next year, stadium-goers displayed large anti-Semitic banners at a match last year, and fans reportedly marched through town with a banner saying "The Aryan hordes are coming."
In Austria, the wall of the Mauthausen concentration camp was defaced in 2009 with a phrase that sums up many sentiments found on Europe's very far-right: "What the Jew was for our fathers, the Moslem brood is for us. Beware!"
Economic hard times and their consequences like high unemployment can breed radicalism on both the left and right, and gave rise to the Nazi party in Germany in the 1920s.
Historians say Europe, despite its current debt woes and immigration tensions, is in better overall shape today, and that the greater risk is of isolated pockets of anger exploding.
"Of course there are big problems, economic, social, political, and cultural ... but we are not in the stage of fascism and we have not had that kind of economic worldwide crisis up to now," said Hajo Funke, political science professor at Berlin's Free University who specializes in the far-right.
Slobodan Lekic in Brussels, David Rising in Berlin, George Jahn in Vienna, Mansur Mirovalev in Moscow, Jim Heintz in Stockholm, Dusan Stojanovic in Serbia, Vanessa Gera in Warsaw, Colleen Barry in Rome and Harold Heckle in Madrid contributed to this report.