US Republican presidential candidate Donald Trump. Reuters/Carlo Allegri Donald Trump is going after Jeff Bezos.

The US Republican presidential candidate said on Thursday that Amazon, the world's biggest online retailer, has "a huge antitrust problem."

In an interview on Fox News, Trump also claimed that Amazon CEO Jeff Bezos — who owns The Washington Post — is using the newspaper to influence politicians in Washington to help Amazon on taxes. (Scroll down to watch the interview.)

"This (Washington Post) is owned as a toy by Jeff Bezos, who controls Amazon. Amazon is getting away with murder tax-wise. He's using The Washington Post for power so that the politicians in Washington don't tax Amazon like they should be taxed," Trump said. "He's using The Washington Post ... for political purposes to save Amazon in terms of taxes and in terms of antitrust."

Trump added: "He thinks I'll go after him for antitrust. Because he's got a huge antitrust problem because he's controlling so much. Amazon is controlling so much of what they are doing."

The Republican presumptive presidential nominee made his remarks in response to the news that The Washington Post has 20 reporters looking into Trump, investigating "every phase of his life," including his real-estate business.

Amazon did not immediately respond to a request for comment.

This isn't the first time Trump has targeted Bezos. In December, he charged that Trump was using The Post as a "tax shelter," baffling many economic experts.

Trump's campaign for president has been bitterly divisive. The reality-TV star has proposed to bar Muslim immigrants and tourists from entering the US, and has accused the Mexican government of sending "rapists" across the border, among other controversial items.

You can watch the full exchange between Donald Trump and Fox News' Sean Hannity below.