WASHINGTON (CNN) - At least 565 individuals have been arrested on allegations they operated phony sweepstakes and lottery contests and a variety of other mass marketing fraud schemes in the United States and four other countries, Justice Department officials announced Tuesday.

Officials said the year-long international investigation targeted schemes that particularly preyed on the elderly, and allegedly resulted in about $1 billion in losses suffered by an estimated 2.8 million victims.

"Operation Global Con" was aimed at taking down operators of a wide range of fraud operations, including schemes involving phony promises of prizes, investment scams, credit card and loan schemes, and other frauds perpetrated through phone calls, mailings, and the Internet, the Justice Department said.

More than half of the arrests - 310 - occurred in Spain, Justice Department officials said, while 139 were in the United States, 96 in Canada, 11 in the Netherlands, and nine in Costa Rica.

Officials said separate law enforcement operations are looking into similar activities in other countries but declined to elaborate.

An official of Costa Rica, where fraudulent operations have been sprouting up, is expected to join Attorney General Alberto Gonzales and officials from the Federal Trade Commission and Postal Inspection Service for a 2 p.m. ET news conference to announce results of their enforcement operation.

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