Former FBI Director James Comey James Brien ComeyDemocrats fear Russia interference could spoil bid to retake Senate Book: FBI sex crimes investigator helped trigger October 2016 public probe of Clinton emails Trump jabs at FBI director over testimony on Russia, antifa MORE blasted his questioning by House lawmakers Friday as part of a GOP-led investigation, saying that they "came up empty today but will try again."

"Today wasn’t a search for truth, but a desperate attempt to find anything that can be used to attack the institutions of justice investigating this president," Comey wrote on Twitter.

"In the long run, it'll make no difference because facts are stubborn things."

Today wasn’t a search for truth, but a desperate attempt to find anything that can be used to attack the institutions of justice investigating this president. They came up empty today but will try again. In the long run, it'll make no difference because facts are stubborn things. — James Comey (@Comey) December 7, 2018

Comey praised Mueller for keeping the special counsel investigation's findings under wraps after leaving his testimony.

"As a private citizen, as someone who knows the justice system, I see it proceeding incredibly quickly and very, very professionally,” he told reporters. “But the most important indication of that is you don't know anything about it except when you file something in court and that's so it should be."

Friday's hearing was mostly attended by Republican lawmakers on the House Oversight and Government Reform Committee and the Judiciary panel, which are jointly investigating alleged bias at the Justice Department and FBI.

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The GOP-led investigation is based on messages unearthed by the Justice Department's inspector general that showed top department officials expressing criticism of President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE before the election.

Comey had been pushing against Republican requests for the hearing for months.

His testimony will be released sometime Saturday and he will be returning for a second session on Dec. 17, while Republicans maintain control of the committees.

Democrats and other critics argue Republicans are seeking to undermine special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE’s investigation into Russian interference in the 2016 presidential election and potential collusion between Trump's campaign and Moscow.

“This was again a frivolous attempt by Republicans to drag old investigations into the limelight,” Rep. Sheila Jackson Lee Sheila Jackson LeeHillicon Valley: Murky TikTok deal raises questions about China's role | Twitter investigating automated image previews over apparent algorithmic bias | House approves bill making hacking federal voting systems a crime House approves legislation making hacking voting systems a federal crime Lawmakers press CDC for guidance on celebrating Halloween during pandemic MORE (D-Texas) told reporters Friday.

Mueller is also said to be examining the circumstances surrounding Comey’s firing in May of 2017 to see whether the president obstructed justice.

-- Updated Dec. 8, 12:56 p.m.