LOS ANGELES (Reuters) - Kathryn Bigelow's snub by Academy Awards voters stunned her cast and awards pundits on Thursday, with some pointing the finger at Washington politicians for the "Zero Dark Thirty" director's omission from the best director Oscar shortlist.

Bigelow was seen as the biggest casualty on Oscar nominations day after her controversial Osama bin Laden thriller won five nods, including best picture, but the director herself was cut out of the running for the industry's biggest honors.

"Kathryn Bigelow was robbed," tweeted Megan Ellison, one of the movie's producers, after the nominations were announced.

The movie about the decade-long U.S. hunt for bin Laden has come under fierce attack in Washington. A group of senators in December chided distributor Sony Pictures in a letter, calling the film "grossly inaccurate and misleading" for suggesting torture helped the United States capture bin Laden in May 2011.

The Senate Intelligence Committee has also launched a review of CIA dealings with Bigelow and screenwriter Mark Boal.

Hollywood watchers say the negative publicity affected the choices made by the Academy of Motion Pictures, whose 6,000 members are working professionals in the industry.

Los Angeles Times film critic Kenneth Turan blamed the snub for Bigelow on what he called Washington bullies.

"Chalk up this year's (Oscar) nominations as a victory for the bullying power of the United States Senate and an undeserved loss for 'Zero Dark Thirty' in general and director Kathryn Bigelow in particular," Turan wrote on Thursday.

Noting that the film has been "almost universally acknowledged as formidable," Turan added that "three members of the Senate, a deliberative body not previously known for its cinematic acumen, decided to place their feet on the neck of this particular film."

Bigelow, who won directing and best picture Oscars in 2010 for her Iraq war film "The Hurt Locker," was silent on Thursday. But Boal, who got a screenplay nod, said pointedly that "none of us would be so honored today without the genius and remarkable talent of Kathryn Bigelow, and to her we are forever grateful."

Bigelow and Boal have said repeatedly that their film shows a variety of intelligence methods that were used to find bin Laden, and have denied being leaked classified material.

Jessica Chastain, who plays a determined young CIA agent credited with tracking down the al Qaeda leader to a house in Pakistan, called her best actress nomination "bittersweet."

"I'm so excited, but I also feel the shock of Kathryn not being nominated," Chastain told entertainment industry website TheWrap.com.

Hollywood awards pundits noted that Bigelow was nominated just two days ago for a Directors Guild award.

Tom O'Neil of Goldderby.com told Reuters the controversy in Washington may have caused a backlash in Hollywood.

But Pete Hammond, awards columnist for website Deadline.com, said the snub for Bigelow could bring a sympathy vote for the movie itself at the February 24 Oscars ceremony.

"Despite the controversy, people may use the snub of Bigelow to make a bigger statement about artists having the right to make the movies they want to make without the interference of the government," Hammond told Reuters.

Speaking at the "Zero Dark Thirty" premiere in Washington on Tuesday, Bigelow said she found the criticism on Capitol Hill "surprising, but I also respect their opinions and I think that unfortunately the film has been mischaracterized."

"Argo" director Ben Affleck, Quentin Tarantino ("Django Unchained") and Tom Hooper ("Les Miserables") were also left off the director shortlist although their films were among the best picture nods.