Roughly three weeks after their arrest in a federal corruption case, Dean G. Skelos, the former majority leader of the New York Senate, and his son were indicted by a grand jury on Thursday on charges of extortion, wire fraud, conspiracy and bribe solicitation.

The accusations in the six-count indictment handed up in United States District Court in Manhattan largely track the six counts in the criminal complaint that was the basis of the May 4 arrests of the senator and his son, Adam B. Skelos.

The indictment, however, includes one additional accusation: that the senator secured over $100,000 in payments and health benefits from a medical malpractice insurer that provided his son with a no-show job while it lobbied the senator on legislative matters.

The 22-page indictment, brought by the office of the United States attorney for the Southern District of New York, does not name the insurer and provides no further details.