Murdoch is under scrutiny for his role in failing to uncover systematic illegal interception of phone calls at the News of the World newspaper, which was shut down last July, and stepped down as chairman of News Corp's UK publishing arm last month.

One document filed this week shows that Murdoch has resigned from the board of Times Newspaper Holdings, which was set up to guarantee the independence of the Times of London and the Sunday Times when News Corp acquired the titles in 1981.

Earlier documents show that Murdoch stepped down from the boards of holding companies News Corp Investments and News International Publishers Ltd shortly after resigning as chairman of News International, News Corp's UK publishing arm.

News Corp declined on Saturday to comment on the resignations.

Murdoch was recently appointed deputy chief operating officer of News Corp and is now based in New York, where he is focusing on the media conglomerate's pay-TV businesses.

This year, he gave up his directorships of GlaxoSmithKline and Sotheby's, but he remains chairman of British satellite broadcaster BSkyB, of which he was formerly chief executive and in which News Corp owns 39 percent.

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