Four men who federal prosecutors said were leading members of the Genovese crime family were arrested yesterday on charges including racketeering, extortion, loan sharking and witness tampering.

The men - Dominick Cirillo, Lawrence Dentico, John Barbato and Anthony Antico - all pleaded not guilty in Federal District Court in Brooklyn yesterday afternoon after their arrests. Prosecutors said Mr. Cirillo, 75, is the acting head of the Genovese family.

"With these arrests, law enforcement has effectively dismantled the present leadership of the Genovese family," the United States attorney in Brooklyn, Roslynn R. Mauskopf, said in a statement announcing the indictments of the men.

Prosecutors charged that the men took over the administration of the Genovese family business when their leader, Vincent Gigante, went to jail in 1997. The men, prosecutors said, continued the family's involvement "in crimes designed to enrich its members," including extortion, loan sharking and fraud.

The arrests come several years after the 2001 indictments of dozens of people who prosecutors say were senior or rank-and-file members of the family. At that time, prosecutors said the arrests represented a serious blow to the family.

An informer inside the family provided secretly recorded conversations that led to the arrests, prosecutors said.

Mathew J. Mari, a lawyer for Mr. Antico, 59, said that the charges announced yesterday were poorly substantiated and vague. The indictments do not describe the charges in detail, providing approximate dates of the crimes without disclosing the names of the victims.

"They wouldn't say who he extorted, nor would they describe the so-called extortions," Mr. Mari said. His client was also charged with trying to tamper with a witness.

A spokesman for the United States attorney's office would not comment on the indictments.

The indictments say that some of the crimes took place five or more years ago. "If these activities described by the government are so dangerous," Mr. Mari said, "how come they are sitting on it for almost five years?"

Mr. Mari said lawyers for the men requested that they be released on bail or placed under house arrest, as several have medical conditions that need tending. Prosecutors asked that the men remain in federal custody without bail.

A judge is scheduled to decide tomorrow whether to set bail, Mr. Mari said.

Prosecutors say that in 2000, Mr. Cirillo convened a panel of Genovese leaders including Mr. Dentico, who is now 81, and Mr. Barbato, now 70, to discuss whether to commit a murder. They decided that the murder should take place, but it was not clear whether it ever did, the indictments said.

Efforts to reach a lawyer for Mr. Cirillo for comment by telephone were not successful. A lawyer for Mr. Barbato, Murray Richman, said only that his client was not guilty.