U.S. President Donald Trump again laced into Jeff Sessions, his attorney general, on Saturday after Sessions defended himself from the president's scathing criticism over his recusal from a probe into Russia's alleged interference in the 2016 election.

In a rare rebuttal to Trump, Sessions said on Thursday that he "took control of the Department of Justice" the day he became attorney general, and that "the actions of the Department of Justice will not be improperly influenced by political considerations."

In a tweet on Saturday morning, Trump replied that Sessions "doesn't understand what is happening underneath his command position."

Special Counsel Robert Mueller, who is running the Russia probe, is "highly conflicted" and "real corruption goes untouched," Trump continued.

Sessions, a former U.S. senator from Alabama, was one of the first Republican lawmakers to back Trump's presidential election bid and has implemented his hardline immigration policies in the role of attorney general.

But Trump has repeatedly criticized Sessions for recusing himself from the Russia probe, including in a Fox News interview taped on Wednesday when he said that Sessions "never took control of the Justice Department."

Trump denies any collusion with Moscow and calls the investigation a "witch hunt."

The back-and-forth between Trump and Sessions has sparked new speculation that Trump might fire Sessions.