ROME, Italy (CNN) -- Italian Prime Minister Silvio Berlusconi appears to be making good on his promise to deal with crime and immigration, launching a nationwide police sweep just weeks after taking office.
An Italian firefighter tries to extinguish a fire at a Roma camp on May 14 in the Ponticelli suburb of Naples.
Yet critics say they are worried it will target people who legally live and work in Italy.
Frustration with illegal immigrants turned to rage last week when an angry mob attacked a Roma gypsy camp outside of Naples.
The rampage started Tuesday, when a gypsy woman was accused of trying to steal a baby from a nearby apartment. Police arrested the woman, but a crowd then turned against all 800 gypsies living in the camp.
"They have to go," said one Italian. "They stink, they bother us, and they steal from us. That is why they have to go."
Tuesday night, a group of people torched the camp, forcing residents to flee under police protection.
Italian Interior Minister Roberto Maroni condemned the incident but acknowledged a growing worry among Italians about illegal immigrants and crime.
"Italians are concerned about their security and we have to give an immediate and efficient answer to their demands regardless of where those who commit the crime come from," he said.
Early Thursday morning came the first step -- a nationwide police sweep targeting streets, houses, and gypsy camps. Police said the raids, which began at 1 a.m., resulted in some 400 arrests, mostly for drug dealing, prostitution, and robbery. Watch police raid Roma gypsies. »
The Interior Ministry says one in three crimes in Italy is committed by a non-Italian. Romanians top the list of non-Italians who commit homicides, sexual assaults, robberies and extortion, the ministry said.
Though police said the raids did not target gypsies, most of those arrested came from Romania and North Africa. And most Roma gypsies who arrived in Italy in recent years have come from Romania, leading many Italians to believe they are the source of crime.
Critics, however, warn that government plans to introduce tougher measures against illegal immigrants may also unfairly target immigrants who live and work in the country legally.
Virginia and Radu are two such legal immigrants, having arrived in Italy six years ago from Romania. They have the right to live and work in the country as long as they are registered with police and can support themselves.
But when police raided their camp last week about 10 miles east of Rome, they arrested more than 30 people and told Virginia she could be expelled.
"I earn 650 euros ($1,012) a month and pay 100 euros ($155) in taxes," Virginia said. "But the police told me I could be sent home because I couldn't live on that salary and support a family of four. With that money, they said, I could live in Romania."
The Interior Ministry has said there will be no mass expulsions of illegal immigrants.