Democratic presidential nominee former Secretary of State Hillary Clinton (L) and Republican presidential nominee Donald Trump listen during the town hall debate at Washington University on October 9, 2016 in St Louis, Missouri.

Playing defense after the latest twist in the Russia investigation, President Donald Trump turned back the clocks Thursday.

In a pair of late-afternoon tweets, Trump railed against his 2016 opponent, Hillary Clinton, questioning why the scrutiny was on him, the president, and not her. Breaking out his campaign nickname for Clinton — "crooked" Hillary — he said the former secretary of State and her family had "dealings" with Russia.

Tweet: Why is that Hillary Clintons family and Dems dealings with Russia are not looked at, but my non-dealings are?

He also questioned why she was not investigated for obstruction last year.

Tweet: Crooked H destroyed phones w/ hammer, 'bleached' emails, & had husband meet w/AG days before she was cleared- & they talk about obstruction?

The tweets came after a Washington Post report that former FBI Director Robert Mueller, the special counsel overseeing the probe into Russian interference in the 2016 election, is also looking into whether Trump attempted to obstruct justice. The obstruction investigation began just days after the president abruptly fired former FBI Director James Comey, according to the newspaper.

In a pair of earlier tweets, Trump called the investigation "phony" and the "greatest WITCH HUNT in American political history."

After the report, Trump's lawyer accused the FBI of an "inexcusable and illegal" leak of information. It is not clear if the bureau was the source of the Post's report.

Clinton and her associates were never charged in the investigation into her use of a private email server and handling of classified information at the State Department.

Trump and other critics have repeatedly accused her and former Attorney General Loretta Lynch of improper conduct in the probe.

Watch: Comey says he knew there was no case regarding Clinton emails