US President Donald Trump on Friday appeared to confirm that he was being probed for firing the FBI chief and described it as a “witch hunt”, as he asserted that there was no proof of his “collusion with the Russians” even after seven months of investigation. “I am being investigated for firing the FBI Director (James Comey) by the man who told me to fire the FBI Director! Witch Hunt,” Trump said in a tweet. Trump's apparent confirmation that he is under probe for obstruction of justice by special counsel appointed to probe alleged Russian meddling in the 2016 presidential polls came a day after a Washington Post report pointed to such an investigation.