Several Italian Mafia bosses have been released from prison under a new coronavirus regulation, the country's national anti-Mafia prosecutor said.

Francesco Bonura, an influential boss in the Sicilian Cosa Nostra; Vincenzo Iannazzo, a member of the Ndrangheta; and Pasquale Zagaria, a member of the Casalesi clan, have now been moved to house arrest, according to Federico Cafiero De Raho, Italy's anti-mafia prosecutor.

To prevent the spread of the novel coronavirus within correctional facilities, the Italian government authorized magistrates to transfer inmates who have 18 months or less in their sentences to house arrest.

Cafiero De Raho said the three men had been held under "extra isolation measures" to avoid contact with people outside the prison because of the roles they had in Mafia organizations.

"Once they are sent back home, these measures are obviously no longer enforced," the prosecutor added.

Bonura was sentenced to 23 years in prison for charges linked to his role in a Mafia organization and was serving only nine more months in prison.

Iannazzo was sentenced in 2018 to more than 14 years in prison for charges of being an accomplice of a Mafia syndicate. He is also known as a powerful clan leader in the city of Lamezia Terme.

Zagaria was arrested in 2007 and sentenced to 20 years in prison as a member of a Mafia organization. He was considered the financial mind behind the Casalesi clan.

The release of Mafia bosses was met with criticism in Italy.

"That is crazy," Matteo Salvini, the leader of Italian opposition party the Lega, said in a Facebook video. "It's a lack of respect for people, magistrates, journalists, policemen and victims of the mafia."

Justice Minister Alfonso Bonafede said the decision to release inmates is taken by magistrates in an "autonomous and independent way" but authorities are considering a proposal to involve the nation's anti-Mafia department in the final decision.

"In this moment of crisis, Mafia organizations can further infiltrate economic life, especially by supporting or even acquiring businesses in financial difficulties that aren't able to access public aid and are therefore obliged to turn to alternative credit sources, those of the criminal organizations," Cafiero De Raho, the prosecutor, told CNN.

The total number of prisoners in Italy has dropped by 6,500 since February 29, according to the Justice Ministry.

Alessio Scandurra, coordinator of Antigone, a prisoner's rights association, said the coronavirus regulations and other factors are behind the decrease in inmate population.