ATHENS, Greece (AP) -- They descended by the hundreds -- black-shirted, bat-wielding youths chasing down dark-skinned immigrants through the streets of Athens and beating them senseless in an unprecedented show of force by Greece's far-right extremists.In Greece, alarm is rising that the twin crises of financial meltdown and soaring illegal immigration are creating the conditions for a right-wing rise -- and the Norway massacre on Monday drove authorities to beef up security.The move comes amid spiraling social unrest that has unleashed waves of rioting and vigilante thuggery on the streets of Athens. The U.N.'s refugee agency warns that some Athens neighborhoods have become zones where "fascist groups have established an odd lawless regime."Greek police on Monday said they have increased security checks at Muslim prayer houses and other immigrant sites in response to the Norway shooting rampage that claimed 77 lives."There has been an increase in monitoring at these sites since the events occurred in Norway," said police spokesman Thanassis Kokkalakis.Greece's fears are shared across Europe. Last week, EU counterterror officials held an emergency meeting in Brussels on ways to combat right-wing violence and rising Islamophobia, warning of a "major risk" of Norway copycats. The massacre by Anders Behring Breivik prompted continent-wide soul-searching about whether authorities have neglected the threat of right-wing extremists as they focus on jihadist terror.Greece, however, may be particularly worrisome because of the intersection of extreme economic distress and rampant illegal immigration, which can create fertile ground for the rise of rightist movements. Immigrant scapegoating has been rife here as unemployment balloons amid economic catastrophe.Even as Greece founders under mountains of debt, illegal immigrants have been streaming into the country across the Turkish border -- turning Greece into the migrant world's gateway to Europe. Last year, Greece accounted for 90 percent of the bloc's detected illegal border crossings, compared to 75 percent in 2009.The UNHCR and Muslim groups say hate crimes have risen sharply, although police do not have hard numbers.The xenophobic rage exploded in May, when youths rampaged through a heavily immigrant neighborhood in broad daylight, knifing and beating foreigners. The attacks left at least 25 people hospitalized with stab wounds or severe beatings. Athens has since suffered a spate of hate attacks by far-rightists.Last November, the leader of a neo-Nazi group won a seat on Athens' city council, with an unprecedented 5.3 percent of the vote.The UNHCR warns of daily attacks by fascist groups in central Athens."There has been a dangerous escalation in phenomena of racist violence targeting indiscriminately aliens, based solely on their skin color or country of origin," the UNHCR wrote in a June report."In certain areas of Athens, cruel and criminal attacks are nearly a daily phenomenon staged by fascist groups that have established an odd lawless regime."Immigrants testify to the growing atmosphere of hostility."I receive threats all the time," Naim Elgandour, the Egyptian-born head of the Muslim Association of Greece, said in an interview."Things have gotten much worse lately. It's an alarm bell from the rest for Europe," he said. "There may be 5,000 hardcore extremists in Athens, by they are gaining sympathy and tolerance by the day."Elgandour said at least 10 makeshift mosques -- basements and coffee shops converted by immigrants to use as prayer sites -- have been damaged in firebomb and vandalism attacks in the past year.Under the strain of fast-growing unemployment and new immigrant arrivals, once middle-class neighborhoods north of the center are turning into a rightist-ridden slums.Police with machine guns guard intersections, white brothel lights line narrow back streets, and young men from violent far-right groups sit casually in squares, sipping cans of beer and hoping to intimidate immigrants.Police spokesman Kokkalakis said violence by far-right groups has seen "periodical increases" but lacked numbers to point to a trend. But he said most cases of violence that appeared to have a "racial component" in Athens turned out to be the result of rivalry between criminal gangs.Analysts argue that once-marginalized extremist groups are gaining a foothold in mainstream society for the first time, filling a perceived gap in law enforcement in crime-ridden neighborhoods, and benefiting from a surge in popular anger against the political establishment.Since winning a seat on Athens City Council, Nikolaos Michaloliakos, head of the violent far-right group Golden Dawn, has tailored his recent rhetoric to the financial crisis."We are living in an enslaved country, financially and nationally," Michaloliakos, a 54-year-old mathematician, told supporters last month, giving a speech under a statue of Alexander the Great."We have a bankrupt economy and the thieving politicians responsible go unpunished," he said. "How long do they think they can keep lying and fooling the Greek people? Whether they like it or not, the hour of Golden Dawn and nationalist revolution is coming."Aristotle Kallis, a professor of modern history at Lancaster University in Britain, studies European fascism. He argued that Greek extremists are losing the stigma of being associated with the 1967-74 far-right dictatorship and becoming more similar other European groups -- sharing ideas and methods on the Internet."Since the 1990s, Greek nationalism has mutated quite substantially," Kallis wrote in an email to the AP, warning of a broader European rise in bigotry."We are ... becoming complacent about a wider, deep and dangerous prejudice against immigrants that is spreading well beyond the constituency of the conventional far-right."