Trump calls Russia investigation a 'disgrace', questions probe's future

US President Donald Trump on Thursday launched a fresh attack on the Russia investigation, branding it a "disgrace to our Nation" a week after he fired his attorney general, raising questions about the probe's future.

"They have found no collusion and have gone absolutely nuts. They are screaming and shouting at people, horribly threatening them to come up with the answers they want," Trump wrote on Twitter.

"They are a disgrace to our Nation and don't care how many lives (they) ruin." The president has frequently lashed out at the probe led by special counsel Robert Mueller into Moscow's interference in the 2016 US elections and whether there was collusion by the Trump campaign.

But his latest missive takes on new significance in the wake of his appointment of Matthew Whitaker, a past public critic of the probe, as acting attorney general replacing the sacked Jeff Sessions.

The move puts Whitaker, Sessions' former chief of staff, in charge of overseeing the Mueller probe.

On Wednesday, Republican Senator Jeff Flake, a critic of the president, and Democratic Senator Chris Coons attempted to introduced a measure to protect Mueller, but it was blocked by Senate Majority Leader Mitch McConnell.

Top Senate Democrat Chuck Schumer has said that if Whitaker refuses to recuse himself from the probe, as Sessions had done, Democrats will seek to attach legislation protecting Mueller to a must-pass spending bill that will be up for consideration in the coming weeks.