India-born former top federal prosecutor Preet Bharara today raised concerns about US President Donald Trump's decision to fire FBI Director James Comey, saying "everyone who cares about independence and rule of law" should be troubled by the move.

Trump fired Comey, saying he was no longer effectively able to lead the bureau and it was necessary to restore "public trust and confidence" in it.

Bharara, 48, who himself was fired by the Trump administration, tweeted, "EVERYONE who cares about independence & rule of law in America should be 'troubled by the timing and reasoning' of Comey firing."

Bharara was one of 46 attorneys Trump asked to resign after taking office. His dismissal had also came as a surprise after the attorney said Trump asked him to remain in his post shortly after the election.