Over the past year, Europe has suffered deadly manifestations of these tensions with the France attacks and the July massacre in Norway carried out by Anders Behring Breivik, who slaughtered 77 people with a bomb in Oslo followed by a shooting rampage at a Labor Party youth camp on an island retreat.
The two horrors have drawn inevitable comparisons.
Both killers had a terrifying sense of theater. Breveik's island rampage, in which he picked off the trapped children one at a time, seemed straight out of a horror movie. The French police account of Merah's last stand, his Colt .45 blazing as he jumped from the balcony, seems inspired by an action film.
Initial reactions to the attacks point to the ambiguities swirling around Europe's immigration debate.
When Breveik's deadly bomb ripped through the Norwegian capital on July 22, many counterterrorism experts assumed Muslim radicals were behind the blast. Similarly, many initially suspected that the French killings might be the work of a far-right fanatic.
The bloodshed carried out by both extremes in the heated immigration debated raises the specter of clashes between the two. There already have been street scuffles between the English Defense League and radical Islamists in Britain — although none has escalated into major violence.
Nicolas Lebourg, a historian who studies the far-right at Perpignan University in southern France, said that both Breivik and Merah were products of an increasingly polarized Europe.
"For people who are a little fragile, people who are a little sensitive ... we're overheating them by telling them that there's this cosmic war between good and evil," Lebourg said.
Associated Press writers Raphael Satter in Paris, Karl Ritter in Stockholm, and Jan M. Olsen and David MacDougall in Copenhagen contributed to this report.
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