A New York grand jury has indicted former US President Donald Trump, making him the first former president to face criminal charges.

The charges remained under seal on Thursday, but the investigation centered on Trump's alleged hush-money payments to a porn star who claims she had an affair with him.

New York prosecutors say they have contacted Trump's attorney to coordinate his surrender to the Manhattan District Attorney's Office "for arraignment on a Supreme Court indictment." Multiple media outlets say Trump could be arraigned next Tuesday.

Trump said in a statement, "This is political persecution and election interference at the highest level in history."

He also said the Democrats have "done the unthinkable" by "indicting a completely innocent person." He called the indictment a "witch hunt" and said it "will backfire massively" on US President Joe Biden.

Observers are focusing on how the indictment will affect Trump's bid for the 2024 presidential election.