U.S. President Donald Trump's Twitter account remained silent during fired FBI director James Comey's testimony on Thursday, but the president's son, Donald Jr., was quite vocal in his father's defence.

Donald Jr. tweeted or retweeted messages more than 60 times during and shortly after Comey's highly-anticipated appearance at the Senate Intelligence Committee hearing.

The president's son frequently disputed Comey's remarks, retweeted factually dubious or false claims and shared television clips from pundits supporting his father.

Trump Jr. focused, in particular, on Comey's statement that he asked a friend to leak one of his memos to the press, after Comey had been fired. The memo contained details of Comey's private conversations with Trump, in which the president allegedly asked for Comey's "loyalty."

Trump's other adult son, Eric, also tweeted and retweeted a handful of messages related to Comey leaking his memo.

President Trump did not tweet at all during the hearing. He also made no mention of it during a speech at a Faith and Freedom Coalition conference in Washington, which took place during Comey's testimony.

The president's wife, Melania, and daughter Ivanka did not tweet about the hearing.