NEW YORK (AP) _ The reputed head of the Colombo crime family pleaded innocent Wednesday to killing an underling.

The charges against Victor ''Little Vic'' Orena were filed in the same federal court where reputed Gambino boss John Gotti was awaiting a jury's verdict on murder, racketeering and other charges.

Orena's arrest means four of the leaders of New York's five crime families are now in jail or awaiting trial, U.S. Attorney Andrew J. Maloney said.

Orena and Pasquale ''Patty'' Amato, a reputed Colombo family captain, were indicted by a grand jury on murder and murder conspiracy charges in the Nov. 3, 1989, slaying of Thomas C. Ocera.

The two pleaded innocent, and U.S. District Judge I. Leo Glasser scheduled a bail hearing Monday. Orena and Amato, both 57, face life in prison if convicted.

''I think we are wreaking havoc on the Cosa Nostra,'' Maloney said at a courthouse news conference.

''The world of omerta (silence) is rapidly evaporating,'' he said. ''Our cup runneth over'' with informants.

Maloney said he hoped the arrests would ''cool the war'' under way within the Colombo family.

Federal authorities say Orena was designated as ''acting boss'' by the Colombos' imprisoned chief, Carmine Persico. They say his attempt to take control on his own touched off a wave of violence in which several alleged mobsters have been killed or wounded.

Besides Orena and Gotti, the other alleged crime bosses under indictment are the Lucchese family's Vittorio ''Vic'' Amuso, jailed awaiting a racketeering trial, and Vincent ''The Chin'' Gigante of the Genovese family, who is under indictment but said to be mentally incompetent to stand trial.

Law enforcement officials say the fifth family, the Bonannos, is nearly defunct.