Showing that fact is stranger than fiction, action hero-turned-Buddhist Steven Seagal sicced the feds on film producer Julius Nasso — accusing his longtime partner of using Gambino muscle to squeeze him for hundreds of thousands of dollars.

Nasso, 49, was hauled off in handcuffs on extortion charges in an early-morning raid on the mob yesterday — charged with demanding $150,000 per movie from the silver-screen muscleman. 

Nasso's 22-year partnership with Seagal dissolved two years ago after the martial-arts master fell under the spell of a Buddhist "spiritual adviser" — who told him it was bad karma to make movies, according to a $60 million suit filed by Nasso in Staten Island. 

The producer has accused Seagal in the suit of breaking a contract to star in four movies — including Genghis Khan, Blood on the Moon, Smash and Grab, and Prince of Central Park — and claims Seagal's pictures have grossed over $1 billion for Warner Bros. 

Nasso would forego the money, however, if Seagal would take the "honorable path" and fulfill his obligations. But the producer hasn't exactly been on the straight and narrow himself, authorities charged yesterday. 

Two weeks ago, Seagal whimpered to a federal grand jury that a crew of mobsters was bullying him, a source said. 

An indictment unsealed yesterday names Nasso as a Gambino associate, and charges him with joining an extortion scheme that targeted Seagal from September 2000 through May 2002 — with the help of his Nasso's brother Vincent, also a mob associate, reputed Gambino capo Anthony "Sonny" Ciccone and wiseguy Primo Cassarino. 

Nasso's lawyer Barry Levin accused Seagal of "sour grapes" and denied the 5-foot-3 film producer ever threatened the star. 

"It is absolutely vindictive. This is a divorce by two men who were in business for 20 years," Levin said, adding that Nasso has never even has a speeding ticket. 

Prosecutors say they caught Ciccone ordering Nasso to demand a $150,000 kickback from Seagal for every action flick he starred in. 

Later, when Ciccone learned Nasso had promised to share the illicit proceeds with other unnamed cohorts, court papers say, Ciccone lashed into him. 

Nasso faces up to 20 years in prison, and was released on $1.5 million bail at an arraignment at Brooklyn federal court. 

"Steven Seagal severed his relations with Mr. Nasso some time ago. The indictment against Mr. Nasso contains no allegations of any wrongdoing or any impropriety of any kind by Mr. Seagal or by any of their former business ventures," said Seagal's lawyer, Martin Pollner.

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