Washington DC - Billionaire Elon Musk, the world's richest man and an avid supporter of Donald Trump, was plunged into new controversy on Friday after a report that he is in regular contact with Russian President Vladimir Putin.

The Wall Street Journal story, which has been denied by the Kremlin, comes just days after the US Justice Department reportedly sent a letter to Musk's America PAC warning that its $1 million giveaways to registered voters may violate federal law.

Musk – the chief executive of SpaceX and Tesla and the owner of X, formerly Twitter – has thrown his millions, time, and outsized influence into sending the former Republican president back to the White House since endorsing him in July.

Musk has reportedly donated $118 million to his personal pro-Trump political action committee, appeared on stage with the Republican presidential candidate at a campaign rally in Pennsylvania, and hosted a series of town halls on his own in the battleground state seen as critical in the November election.

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Musk, who once supported Barack Obama but has become increasingly conservative in recent years, peppers his more than 202 million followers on X with a daily stream of political messages championing Trump and denigrating his opponent, Democratic Vice President Kamala Harris.

Many of the X posts by the South African-born billionaire decry the number of undocumented immigrants crossing into the US from Mexico or echo discredited conspiracy theories.

If he wins the election, Trump has pledged to tap Musk to head a "government efficiency commission" tasked with slashing bureaucracy and waste.

Musk already holds a top secret clearance because of the activities of SpaceX, which launches rockets for NASA and the Pentagon, and the Wall Street Journal said his alleged secret contacts with Putin "raise potential national security concerns among some in the current administration."

At the same time, the newspaper said, "No alerts have been raised by the administration over possible security breaches by Musk."

The Journal said the conversations between Musk and Putin touched on "personal topics, business and geopolitical tensions," although at one point the Russian leader asked the billionaire to avoid activating his Starlink satellite internet service over Taiwan as a favor to Chinese President Xi Jinping.

Kremlin spokesman Dmitry Peskov rejected the report on Friday, saying, "It's all untrue, absolutely false information."

Putin had one contact with Musk before 2022, Peskov said, when they spoke on the phone.

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"It was a fact-finding conversation. They talked about more visionary technology, about technology for the future," he said.

SpaceX's Starlink has been a vital communications tool for Ukrainian forces battling Russian troops and Musk "categorically" denied earlier this year that any terminals had been sold to Russia.

"My companies have probably done more to undermine Russia than anything," Musk said during a streamed event on X.

SpaceX has taken away two-thirds of Russia's space launch business and "Starlink has overwhelmingly helped Ukraine," he said.