Trump scaring critics into silence: Brennan

Former CIA Director John Brennan said yesterday he would not be silenced by Donald Trump, a day after the US president revoked the Obama-era official's security clearance and said the move was directly tied to the ongoing Russia investigation.

The Republican president said in a statement on Wednesday that he revoked Brennan's authorisation for making what he called "unfounded and outrageous allegations" about his administration and was evaluating whether to strip clearances from other former top officials. Brennan and the others have been critical of the president.

Trump later told the Wall Street Journal his decision was connected to the ongoing federal probe into alleged Russian interference in the 2016 election and allegedly collusion by his presidential campaign.

"I call it the rigged witch hunt, (it) is a sham," Trump said in an interview with the newspaper on Wednesday. "And these people led it."

"It's something that had to be done," Trump added.

The president has denied any collusion. Russia has said it did not interfere, contrary to the US intelligence community's findings.

Brennan, who led the Central Intelligence Agency under Democratic President Barack Obama, yesterday called Trump's denials "hogwash" and vowed not to be silenced.

"The only questions that remain are whether the collusion that took place constituted criminally liable conspiracy, whether obstruction of justice occurred to cover up any collusion or conspiracy, and how many members of 'Trump Incorporated' attempted to defraud the government by laundering and concealing the movement of money into their pockets," Brennan wrote in an op-ed published in the New York Times.

Former US Director of National Intelligence James Clapper, another critic whose clearance Trump said he might target, cautioned that Brennan was expressing "an informed opinion." It remained up to Special Counsel Robert Mueller, who is leading the probe, to make a final conclusion, Clapper said.