Washington: US President Donald Trump says that although he has never obstructed justice in the Russia investigation, he does "fight back".

And, as of Wednesday, he had "fought back" against a majority of top officials involved in leading, overseeing or making administration decisions about that probe. According to an analysis by The Washington Post, of the more than a dozen officials with what could be construed as leadership roles in the investigation, more than half have been fired and/or threatened with official recourse.

Former CIA Director John Brennan led widespread criticism of Trump, blasting his performance as "treasonous". Credit:AP

The most recent examples were the White House's revocation of former CIA director John Brennan's security clearance on Wednesday and the threats to do the same for nine other current and former officials who have run afoul of Trump. In one fell swoop, the White House effectively more than doubled its enemies list - and served notice that ex-officials who were involved in the probe will not be permitted to criticise Trump willy-nilly.

Not all the firings have come directly from Trump or relate directly to the probe; FBI officials Andrew McCabe and Peter Strzok, for instance, were terminated by the bureau after highly critical inspector-general reports, and former acting attorney-general Sally Yates refused to defend Trump's travel ban in court. But Trump has targeted all of them, and all three also saw their security clearances threatened Wednesday (even as McCabe and Strzok don't appear to have them any more).