MADRID, Spain - The unrest that has gripped Greece for days, sparked by the police killing of a teenager, is spilling over into other parts of Europe, raising concerns that a broader discontent over globalization and economic turmoil is now stoking it.

Protesters in Spain, Denmark and Italy smashed shop windows, pelted police with bottles, and attacked banks this week, while in France, cars were set ablaze yesterday outside the Greek Consulate in Bordeaux, where protesters scrawled graffiti warning of an "insurrection."

At least some of the protests were organized over the Internet, showing how quickly the message of discontent can be spread, particularly among tech-savvy youth.

One Web site that Greek protesters used to update one another on the locations of clashes asserted there have been sympathy protests in nearly 20 countries. More demonstrations were set for today in Italy, France and Germany.

The clashes have been isolated so far and nothing of the scope of the chaos in Greece, which has ballooned into nightly scenes of burning street barricades, looted stores and overturned cars.

Still, authorities in Europe worry conditions are ripe for the contagion to spread.

As Europe plunges into recession, unemployment is rising, particularly among the young. Even before the crisis, European youths complained about difficulty finding well-paid jobs - even with a college degree.

In Greece, demonstrators handed out flyers yesterday listing their demands, which include the reversal of public-spending cuts that have brought more layoffs, and they said they were hopeful their movement would spread.

"We're encouraging nonviolent action here and abroad," said Konstantinos Sakkas, 23, a student at Athens Polytechnic, where many of the demonstrators are based.

Across the continent, Internet sites and blogs have popped up to spread the call to protest.

Several Greek Web sites offered protesters real-time information on clash sites, where demonstrations were heading, and how riot police were deployed around the city. Protest marches were arranged and announced on the sites and via text messages on cell phones.

In Spain, an anti-globalization Web site, Nodo50.org, said: "We stand in solidarity" with the Greek protesters.

One writer on the site london.indymedia.org exhorted people to follow the Greek example and "reclaim the streets. Burn the banks that robbed you."

In France, protesters set fire to two cars and a garbage can filled with flammable material outside the Greek Consulate in Bordeaux yesterday and scrawled graffiti threatening more unrest, Greek Consul Michel Corfias said.

"What's happening in Greece tends to prove that the extreme left exists, contrary to doubts of some over these past few weeks," French Interior Ministry spokesman Gerard Gachet told the Associated Press.

A rally outside the Greek Embassy in Rome turned violent Wednesday, with protesters' damaging police vehicles, overturning a car and setting a trash can on fire.

In Denmark, riot police were pelted with bottles and paint in downtown Copenhagen; 63 people were detained and later released.

In Spain, youths attacked banks, shops and a police station in Madrid and Barcelona late Wednesday. Some of the protesters chanted "Police killers" and other slogans. Eleven people - including a Greek girl - were arrested at the two rallies, which drew about 200 protesters.

Daniel Lostao, president of the state-financed Youth Council, an umbrella organization of Spanish youth groups, said young people in Spain faced daunting challenges - soaring unemployment, low salaries and difficulty in leaving the family nest because of expensive housing.