Philadelphia, Pennsylvania - Philadelphia's chief prosecutor sued billionaire Elon Musk and his pro-Trump political action committee on Monday to halt his $1-million giveaways to registered voters.

The lawsuit against the SpaceX and Tesla CEO's America PAC was filed in a Pennsylvania state court by district attorney Larry Krasner, a Democrat.

"The Philadelphia district attorney is charged with protecting the public from public nuisances and unfair trade practices, including illegal lotteries," Krasner said in a statement.

"The DA is also charged with protecting the public from interference with the integrity of elections," he said.

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Last week, the Justice Department sent a letter to Musk's America PAC warning that its $1-million giveaways may violate federal law, which prohibits paying people to register to vote.

Musk (53), who also owns X, formerly Twitter, has thrown his millions, time, and considerable influence into backing Republican presidential candidate Donald Trump since endorsing him in July.

Musk has reportedly donated $118 million to his personal pro-Trump political action committee, an organization which collects funds for elections.

He's also appeared on stage with Trump 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.

Musk, who previously supported Barack Obama but has become increasingly rightwing in recent years, peppers his 202 million followers on X daily with messages championing Trump and denigrating Democratic Vice President Kamala Harris.