A US millionaire is to appear in court on Friday charged in the murder of a man recruited to build tunnels at his home near the US capital for protection against North Korea, reports say.

Daniel Beckwitt, a conspiracy theorist and millionaire stock trader, has posted a $100,000 bond and will be released from detention on Monday morning, WRC-TV said.

 

Beckwitt, 27, is charged with second-degree murder and involuntary manslaughter in connection with the death in September 2017 of Askia Khafra, 21.

Khafra died when a fire broke out in the basement as he dug a tunnel under the home where Beckwitt lived in Bethesda, Maryland, a Washington suburb.

Beckwitt is "an unusual individual," his lawyer Robert Bonsib told court on Thursday when a grand jury indicted the millionaire, The Washington Post reported.

Beckwitt, set to appear in court on June 8, sought to "create a secure bunker because of his concern about international tensions, North Korea, intercontinental ballistic missiles," Bonsib said.

WRC-TV showed earlier footage of what it said was Beckwitt -- his identity hidden under a shiny gold outfit and hood resembling a firefighter's protective suit -- addressing a computer hacking convention.

Beckwitt spoke of "legislative creepings by our misguided government toward the Orwellian tyranny... powered by signals intelligence."

Khafra reportedly met Beckwitt through social media, and was told "if he digs in this tunnel, day and night, and sleeps in this tunnel, and eats in this tunnel, and goes to the bathroom in buckets in this tunnel, he will be compensated financially so he can start his dream company," Montgomery County assistant state's attorney Doug Wink told court, according to WJLA-TV.

Beckwitt allegedly picked up Khafra from his home elsewhere in Maryland, made him wear dark glasses and drove him on a roundabout route to hide the project location, the Post reported, citing a court document.

The tunnels reportedly began at the base of a 20-foot (three meter) shaft below the basement and branched out about 200 feet.

The prosecution alleges that piles of junk in the house and basement, as well as a "daisy-chain" of power cords in the tunnels, made the project unsafe.

"You were essentially acting in a way that you were disregarding human life," Montgomery County state's attorney John McCarthy told reporters.

Khafra died during a period of high tension between the United States and North Korea, leading to fears of war over that country's nuclear weapons and ballistic missile programs. (AFP)