A man who approached police holding a mysterious "cylindrical object" has been shot dead following a car chase through a top secret nuclear test site.

The unnamed man burst past a security checkpoint at the Nevada National Security Site (NNSS), 65 miles northwest of Las Vegas, late on Monday afternoon, prompting private security contractors and local police to give chase.

The pursuit lasted around eight miles, the Department of Energy said in a statement, before the man pulled over, got out of the car, and approached the officers while holding a “cylindrical object”.

After failing to listen to police orders, he was shot and died at the scene.

The department said the FBI had been called in to help investigate the incident.

The closely guarded facility, previously known as the Nevada Proving Grounds, covers almost 1,400 square miles of desert in the western state, and was the site of hundreds of nuclear weapons tests during the Cold War.

As well as nuclear testing sites, the NNSS includes a nuclear weapons assembly factory, an experimental test flight centre, and a nuclear waste disposal site.

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As recently as 2012, it was used to conduct an underground explosion involving radioactive plutonium.

Last year, the state of Nevada sued the Trump administration over its plans to store more than a metric ton of plutonium at the site, citing health concerns and the environmental impact.

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The NNSS is located around 30 miles west of the far more notorious site, Area 51 - a remote military testing facility subject to countless UFO-based conspiracy theories.