WASHINGTON, May 17 (Xinhua) -- U.S. President Donald Trump ripped the Russia probe led by special counsel Robert Mueller on Thursday, the day that marks the one-year anniversary of Mueller's appointment.

"Congratulations, we are now into the second year of the greatest Witch Hunt in American History," Trump tweeted in a sarcastic tone.

"There is still No Collusion and No Obstruction," said the president, reiterating his signature description of the year-long investigation.

Mueller was appointed exactly a year ago by Deputy Attorney General Rod Rosenstein following Trump's firing of Federal Bureau of Investigation (FBI) Director James Comey to investigate the alleged Russian interference in the 2016 U.S. presidential election and any potential collusion between the Trump campaign and Moscow.

The mandate also allowed the special counsel to look into related matters that may arise from the investigation that was therefore expanded to include an effort to see if the president has tried to obstruct justice.

Over the past year, Mueller's team has brought charges against 19 individuals, including several Trump campaign associates, and three Russian entities, notched five guilty pleas and seen one person sentenced.

A number of those charges was related to Russia's alleged interference in the 2016 election, but none of them has been extended to collusion allegations.

Russia has denied interference in the election campaign.

Trump, who has reshuffled his legal team, has ratcheted up pressure on the Mueller-led probe in the past months.

Trump's lawyer Rudy Giuliani said Wednesday that Mueller's team has informed the president's lawyers that it would follow Justice Department guidance and not seek an indictment against Trump.

Mueller's team has declined to comment.