Hundreds of Italian police early Monday carried out raids and checks of far left groups after scores of people were injured in Rome's worst street violence in years, officials said.
What started out as a demonstration joining a global day of protests against corporate greed and budget cuts on Saturday degenerated into urban warfare between protesters and police, leaving 135 injured including 105 police.
Damage to public property was estimated at around one million euros ($1.4 million).
Interior Minister Roberto Maroni condemned the "unprecedented violence" and thanked law enforcement for ensuring there were no fatalities.
"There was a real risk of this because the violent protesters were using the march as a shield," Maroni said, adding: "I want the authors of this violence, who are real dyed-in-the-wool criminals, to pay as an example to others."
The weekend clashes were the worst in Rome since the violent and sometimes deadly confrontations pitting political militants from both the far left and the far right against security forces during a period known as the "Years of Lead" in the 1970s and 1980s.