Donald Trump has warned ousted FBI Director James Comey not to talk to the media, a highly unusual move that prompted fresh charges the president is trying to silence the man who led an investigation into possible collusion between Trump's election campaign and Russia.

On Twitter, Trump appeared to suggest that if Comey gave his version of contacts between them, the administration might produce tapes of conversations, although it was not clear if such tapes exist.

The veiled threat added to the storm over Trump's abrupt firing of Comey on Tuesday.

Critics have assailed Trump for dismissing the FBI chief at a time when the agency is investigating alleged Russian meddling in the 2016 US election, and possible Moscow ties to the Trump presidential campaign.

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