Washington: US President Donald Trump on Thursday mocked federal investigators for making up a “phoney collusion with the Russians story” amid new reports that Robert Mueller, the special counsel, is looking into whether Trump tried to obstruct justice in the case.

“They made up a phoney collusion with the Russians story, found zero proof, so now they go for obstruction of justice on the phoney story. Nice,” Trump tweeted just before 7am.

In a second tweet a few minutes later, the president once again called the Russia investigation a “witch hunt” and called the people leading it “very bad,” apparently a reference to Mueller and others at the FBI.

Mueller has requested interviews with three current or former senior intelligence officials, according to a person briefed on the investigation. The move suggests he is examining whether the president sought their help in trying to get James Comey, the former FBI director, to end an investigation into Michael Flynn, the former national security adviser.

The special counsel is also seeking documents from the National Security Agency relating to the intelligence agency’s interactions with the White House on the Russia investigation.

Together, the requests from Mueller suggest new scrutiny on whether the president tried to influence the Russia investigation through conversations he had with Comey, whom he ultimately fired, or with other officials.

That would make Trump a subject of a sprawling inquiry that he has repeatedly said has no merit. During a Rose Garden news conference last Friday, the president insisted that Comey was “a leaker” of information and said that Comey’s testimony on Capitol Hill helped clear the president of wrongdoing.

“Yesterday showed no collusion, no obstruction,” Trump said of Comey’s testimony.

The president’s tweet Thursday morning suggests he remains dismissive of the investigation. Trump reportedly considered firing Mueller as special counsel, but was talked out of it by aides who worried about the consequences of taking such an action.

Christopher Ruddy, a longtime friend of Trump’s, had said publicly that Trump was considering terminating Mueller. Ruddy said the president believed that Mueller had conflicts of interest that should have made him ineligible to lead the investigation.