U.S. President Donald Trump has called the probe into alleged collusion between his 2016 election campaign and Russia "the greatest political crime" in American history, claiming the "scam" was orchestrated by the Barack Obama administration.

In an interview with Fox News on Sunday, Trump also called former National Security Adviser Michael Flynn, who pled guilty of lying to the FBI in 2017, a hero, claiming that the FBI wanted Flynn to make up a story about the Trump campaign.

Stating that no other president should go through what he went through, Trump said "a lot of people are going to have to pay."

Trump's remarks come after the Justice Department moved to drop charges against Flynn, who was previously indicted for falsely testifying about contact with Russia's ambassador to the U.S.

Criticizing top Obama administration officials for requesting to "unmask" the identity of Flynn and others linked to the scandal, Trump called it corrupt, claiming that the former president was well aware of the surveillance.

During an online commencement address to graduates of historically black colleges and universities on Saturday, Obama took an apparent jab at the Trump administration for its insufficient COVID-19 response.

The former president said the pandemic has finally torn away the curtain on the idea that many in charge know what they are doing, adding that many of them are not even pretending to be in charge.