By Barry Moody
ROME (Reuters) - A political storm erupted on Monday over the worst riots in Rome for years, with the government accused of failing to prevent well organized and violent groups infiltrating one of many global protests against the financial system.
While politicians from the fragile government of Silvio Berlusconi used the riots as a stick with which to beat the center-left opposition, accusing them of fomenting discontent, Interior Minister Roberto Maroni came under fire from all sides
for failing to prevent the violence.
The Rome demonstration was the only one to turn violent in an international "day of rage" on Sunday against bankers and governments blamed for the world economic downturn.
Riot police were outflanked and overwhelmed by hundreds of masked and helmeted demonstrators using rocks, petrol bombs and clubs previously hidden along the route.
Only 12 rioters were arrested though police were studying video footage to try to identify about 100 others. Outraged demonstrators from the peaceful march and other Romans handed photos and videos to the police. Some of them fought the rioters on Sunday.
Police carried out raids in several cities during the day and searched youth centers known to have leftist and anarchist sympathizers, officials said.
A van carrying young people was stopped along a highway in central Italy and gas masks and other objects were found that police suspect were used during the Rome riots, the Italian news agency Agi reported.
Damage from attacks on banks, shops, government buildings and churches was estimated at least 2.5 million euros ($3.4 million). Rioters used street signs as battering rams to smash windows.
Berlusconi's government, racked by internal disputes, survived a tense confidence vote on Friday but the billionaire businessman is widely expected to be toppled within months.
His approval ratings have plummeted because of a string of lurid sex scandals and his government's failure to stimulate a chronically stagnant economy.
Several of his key allies sought to exploit the violence to bolster the center-right coalition.
But opposition politicians said Italy's secret service had warned well ahead of time that anarchists and other radicals from the so-called "black bloc" movement were targeting a demonstration by tens of thousands of "indignant" protesters.
They demanded to know why the rioters, many from outside Rome, were allowed to get near the demonstration where they caught police unawares, using rapid movement and tactics including two "columns" and staging a diversionary feint.
The black bloc radicals, named for the helmets and face masks they wear, first emerged in Italy at violent demonstrations against a G8 meeting in Genoa a decade ago when one was killed by police. Like protesters elsewhere they use social media and email to organize.
Many were said to have trained during violent protests this year against a high-speed rail link to France.
"Saturday was a terrible day, perhaps the worst that Rome can remember for many years. But above all it was inexplicable," said Renata Polverini, governor of the Lazio region around Rome.
"We need to understand why all these violent people, some from other parts of the world, decided to come to Rome, and how they arrived without anybody realizing."
Maroni said it was lucky nobody died and praised the security forces. But police unions also criticized him, saying government cuts had left them on low wages, without fuel for their vehicles and robbed of overtime.
One Carabinieri paramilitary policeman identified only as "Fabio" told reporters he was lucky to survive after his armored riot truck was ambushed and set on fire. He suffered a broken nose as he escaped the truck engulfed in flames.
One 30-year-old black bloc rioter told La Repubblica newspaper: "We won because we had a plan, an organization."
He said the rioters divided into two columns, the second held in reserve until late in the day so police misjudged their numbers. Organized into groups of 10 or 15, they were able to slip in and out of the demonstration by removing helmets and masks.
The rioters positioned stockpiles of weapons including clubs, glass marbles and petrol bombs in locations marked by white plastic bags.
The Rome demonstration, which by some estimates involved 200,000 people, was the biggest in the weekend of global protests. It was fueled by resentment and despair at the government's failure to produce viable plans to restore growth to an economy at a virtual standstill for more than a decade.
This mood has been aggravated by a 60 billion euro ($83 billion) austerity plan including increases in taxes and the cost of healthcare. Italy's youth unemployment, at 28 percent, is one of the highest in the euro zone.
Rome Mayor Gianni Alemanno said that as a preventive measure, he had ordered a ban on all demonstrations in the center of Rome for a month.
Maroni, a rising star in Berlusconi's coalition ally the separatist Northern League, will address parliament on Tuesday. He promised draconian punishment for the rioters as well as measures to improve the police response.
($1 = 0.721 Euros)
(Additional reporting by Philip Pullella; Editing by Sophie Hares)