Former U.S. Special Counsel Robert Mueller on Wednesday defended the integrity of his Russia investigation during a dramatic congressional hearing and reiterated that he had not cleared President Donald Trump of obstruction of justice or, as the president has said, totally exonerated Trump.

Mueller appeared for eagerly anticipated testimony at the first of two back-to-back congressional hearings that carry high stakes for Trump and Democrats who are split between impeaching him or moving on to the 2020 election.

The former FBI director, who spent 22 months investigating Russian interference in the 2016 U.S. election and Trump's conduct, appeared first before the House of Representatives Judiciary Committee.

The committee's Democratic chairman, Jerrold Nadler, praised Mueller and said no one, including Trump, is "above the law." But Republicans tried to paint Mueller's investigation as unfair to Trump, with conservative congressman Louie Gohmert heatedly telling him "you perpetuated injustice."

Trump has claimed that the Mueller inquiry resulted in the president's "complete and total exoneration." Asked by Nadler if he had exonerated Trump, Mueller said, "No."

Mueller, accused by Trump of heading a "witch hunt" and trying to orchestrate a "coup" against the Republican president, said his inquiry was conducted in "a fair and independent manner" and that members of the special counsel's team "were of the highest integrity." Trump has accused Mueller of having conflicts of interest. Mueller noted that Justice Department ethics officials confirmed he had no such conflicts.