Fired FBI Director James Comey has tweeted a Bible passage on the same morning that former national security adviser Michael Flynn pleaded guilty to lying to federal agents.

quoting the Old Testament book of Amos, said: "But justice roll down like waters and righteousness like an ever-flowing stream."

Comey was fired in May by President Donald Trump, a move that helped lead to the appointment of Robert Mueller as special counsel.

Comey has said Trump asked him during a private Oval Office meeting in February if he could see his way to letting the Flynn investigation go. The White House has denied that that conversation took place as Comey has said.