Donald Trump has appeared to confirm he is under investigation for obstruction of justice, claiming he is being probed for firing FBI director James Comey by the man who told him to do it.
It was not clear whether the president was basing his tweet on direct knowledge, or on reports this week that special counsel Robert Mueller is examining whether he obstructed justice by firing Mr Comey last month amid the Russia investigation.
Mr Mueller was appointed as special counsel to investigate Moscow's involvement in the presidential election last year and possible collusion by Trump campaign associates with the Russians, but there has been no indication that Mr Mueller told the president to fire Mr Comey.
Mr Trump tweeted: "I am being investigated for firing the FBI Director by the man who told me to fire the FBI Director! Witch Hunt."
Deputy attorney general Rod Rosenstein submitted a widely circulated memo to the president last month raising concerns over Mr Comey's performance, but Mr Trump later said he had already made the decision to fire Mr Comey.
The White House confirmed Mr Mueller was among the candidates the president interviewed to replace Mr Comey. A day later, Mr Rosenstein appointed Mr Mueller, who was at the helm of the FBI during the September 11 attacks, as special counsel.
The new tweets are the latest in a week of angry social media responses from the president over a report by the Washington Post that Mr Mueller was looking into whether Mr Trump obstructed justice.
In a series of statements on Twitter on Thursday, Mr Trump repeated his claim that Mr Mueller's investigation is a "WITCH HUNT" based on the "phony" premise of possible collusion between Russia and a cadre of Trump campaign associates.
The president complained the probe is unfair and wondered why his defeated Democratic opponent was not getting the same scrutiny.
"Why is that Hillary Clintons family and Dems dealings with Russia are not looked at, but my non-dealings are?" he asked.
"They made up a phony collusion with the Russians story, found zero proof, so now they go for obstruction of justice on the phony story. Nice.
"You are witnessing the single greatest WITCH HUNT in American political history - led by some very bad and conflicted people! #MAGA."
The Twitter attacks came as vice president Mike Pence hired a personal lawyer to represent him in the intensifying investigation.
Mr Pence's office confirmed he had retained Richard Cullen, a former Virginia attorney general and US attorney for the Eastern District of Virginia, to assist "in responding to inquiries" from Mr Mueller.
The investigation appears to be reaching a broadening circle of current and former officials.
The Washington Post reported on Wednesday that investigators were looking into possible obstruction of justice. The newspaper noted Mr Mueller had requested interviews with CIA director Dan Coats, National Security Agency chief Michael Rogers and Richard Ledgett, the former NSA deputy director.
Recent news reports have suggested Mr Trump sought all three officials' help in pressuring Mr Comey to drop his investigation into former national security adviser Mike Flynn.
Mr Comey gave evidence last week that he also felt pressured to drop the Flynn probe. He said he believes Mr Trump ultimately fired him "because of the Russia investigation".