Former Philippine president Ferdinand E. Marcos and his wife, Imelda, are targets of a federal grand jury investigation into whether they illegally acquired hundreds of millions of dollars worth of New York real estate and fraudulently attempted to transfer it to Saudi billionaire Adnan Khashoggi in violation of a court order, according to sources familiar with the investigation.

The sources said the U.S. attorney's office in Manhattan is also considering a broader racketeering case including claims that the Marcoses illegally acquired millions of dollars worth of jewelry brought into the United States when they fled the Philippines in February 1986.

Richard A. Hibey, the couple's lawyer, confirmed that Ferdinand Marcos is a target of the New York grand jury. He refused to say whether it also is probing the finances of Imelda Marcos.

He said the Marcoses "deny any wrongdoing" in connection with the New York properties as well as "any wrongdoing with regard to property brought into the country."

In papers filed in federal court in Hawaii last month in a separate case involving ownership of the jewelry and other valuables, government lawyers revealed that the grand jury had subpoenaed the jewelry -- an 18-page listing of sapphire, diamond, emerald, gold and pearl tiaras; necklaces; bracelets; earrings, and other pieces.

The sources said prosecutors are investigating whether the jewelry, some of which Imelda Marcos allegedly bought on shopping sprees in the United States, was acquired with funds illegally diverted from the Philippine government.

On Friday, government lawyers in Hawaii filed papers saying that "there is no way of knowing how long the grand jury will examine the merchandise or when the merchandise will be returned, if ever."

They cited provisions of the federal racketeering law that permit the government to seek to force those convicted of racketeering to forfeit proceeds of their criminal "enterprise."

The sources said the Marcoses were informed by letter this summer that they were targets of the grand jury. Although such a letter is normally the prelude to an indictment, the sources cautioned that no final decision has been made on whether to proceed and that any such action must be cleared by the White House because of its foreign policy implications.

Although several other federal grand jury probes involve Marcos and the Philippines, the New York investigation is the only one in which Marcos has been told that he is a target, sources said.

Federal prosecutors are focusing on four Manhattan office buildings, sources said.

New York real estate agents Joseph and Ralph Bernstein said at a congressional hearing last year that they arranged for the Marcoses to purchase the properties, worth an estimated $326 million at the time of the hearing, through foreign corporations in Panama, the British Virgin Islands and the Netherlands Antilles that shielded the Marcoses from New York state's gains tax.

The Philippine government is attempting to recover the properties in a separate civil lawsuit against the Marcoses, alleging that they were acquired with misappropriated Philippine funds.

The Bernsteins also are suing the Marcoses, alleging that corporations owned and controlled by the couple agreed to sell the brothers three of the buildings in July 1985.

The Philippine government and the Bernsteins allege that the Marcoses and their associates conspired with Khashoggi and his employes to portray Khashoggi as the properties' owner.

They say that in May 1986, after a federal judge prohibited transfer of the properties, Gliceria Tantoco, a Philippine national and close friend and business associate of the Marcoses, backdated a declaration of trust to make it appear that Khashoggi had owned two of the properties since August 1985.

In an affidavit filed in the civil case in New York, Joseph Bernstein states that Karl Peterson, who works for Khashoggi, "told me . . . when he first appeared on the scene in May 1986 . . . that he intended to prepare fraudulent documentation purporting to show Khashoggi ownership dating back to August 1985."

Khashoggi is an arms dealer who provided financing for the U.S. sale of arms to Iran that helped to ignite the Iran-contra scandal.

The complex and far-ranging investigation, directed by Assistant U.S. Attorney Charles G. LaBella, has several other prongs.

In an indictment unsealed in New York in August, Tantoco, her brother-in-law Hector R. Tantoco and their export company, Sanmar, were indicted on charges of conspiring to defraud New York city and state of more than $490,000 in taxes owed on the so-called "Samuels Collection" of art work and other contents of an apartment.

Philippine government sources said that Gliceria Tantoco purchased the $6 million collection for Imelda Marcos and that pieces from it were found by Philippine government representatives in Imelda Marcos' Manhattan townhouse after the Marcoses fled the Philippines to Hawaii, where they now live.

Gliceria Tantoco is being held in Italy awaiting extradition, and sources said prosecutors hope to obtain her cooperation in the grand jury probe.

Prosecutors also are seeking French authorities' help in having returned to the United States more than a dozen paintings by old masters, including a Rubens and two Franz Hals, for use as evidence in the grand jury investigation, sources said.

The paintings, which had hung in the Malacanang presidential palace in Manila or the New York townhouse, were found in a Paris warehouse after authorities searched Khashoggi's Cannes apartment.

The Philippine government is seeking return of the paintings, some of which were bought in the name of the Metropolitan Museum of Manila, claiming that they are Philippine government property.

Prosecutors are also investigating the Marcoses' use of the California Overseas Bank, owned by a close Marcos associate, Roberto S. Benedicto, the sources said. Benedicto's lawyer, Wayne Smith, said prosecutors had informed him that Benedicto was a target of the New York probe. "We don't think they have a case that involves the bank," Smith said.

In a civil racketeering lawsuit in California against the Marcoses, Benedicto and others, the Philippine government claims that he and the Marcoses violated federal mail- and wire-fraud laws and laws against interstate transportation of stolen property by using the bank to transfer money illegally from the Philippines to the United States.

In pretrial discovery, a bank official admitted to Philippine lawyers that accounts were established in the names of fictitious individuals to handle funds believed to belong to Marcos.

The Philippine government claims that some of the money used to purchase one of the New York properties originated in the Philippines at a bank controlled by Benedicto and was transferred from there to the California bank, then to a Swiss bank and back to New York to purchase the building.

The Marcoses' lawyer Hibey said there is "no validity to those allegations" involving the bank.