UPDATE 1-Ford fires CEO Mark Fields, Hackett takes reins - reports

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DETROIT, May 22 (Reuters) - Ford Motor Co Chief Executive Mark Fields is set to leave the carmaker as part of a shake-up that includes other top executive changes as the company's shares hover near a 52-week low, several media reported on Monday.

Forbes and the New York Times reported James Hackett, head of the Ford unit that works on autonomous vehicles, would take the reins. An announcement could come as early as Monday.

Ford shares are down nearly 40 percent since Fields, 56, took over three years ago at the peak of the U.S. auto industry's recovery. Now, U.S. auto sales are slipping, and Ford's profit margins are trailing those of larger rival General Motors Co.

Ford's board of directors and chairman Bill Ford Jr. had been unhappy with the company's performance, and sought more reassurance that investments in self-driving cars, electric vehicles and ride services would pay off.

Details of further executive moves were not clear on Monday. The Wall Street Journal reported on Sunday that the company was considering new assignments for some of Fields' top lieutenants.

"We are staying focused on our plan for creating value and profitable growth," a Ford spokesman in Europe said in response to the reports. He declined to comment "on speculation or rumors."

The turbulence at Ford comes as all three Detroit automakers are under pressure to prove they can avoid losses as the U.S. auto market, source of the bulk of their profits, is slowing down after last year's record sales.

GM Chief Executive Mary Barra is fending off attacks from hedge fund Greenlight Capital and its leader, David Einhorn, who wants to install three new directors on the automaker's board, and split GM's stock into two classes.

FiatChrysler Automobiles NV is fighting accusations by U.S. and California regulators that it used software to cheat on diesel emissions tests, and Chief Executive Sergio Marchionne has so far been unsuccessful in his effort to find a merger partner for the company. (Reporting by David Shepherdson and Joe White in Detroit, Ismail Shakil in Bengaluru, Andreas Cremer in Berlin; Editing by Edwina Gibbs)