Washington (AFP) - The US Justice Department on Friday named a former war crimes investigator as a special counsel to oversee criminal probes into Donald Trump, three days after the former president announced a new White House run in 2024.

Trump – who claims to be the target of a “witch hunt” – slammed the dramatic move as “unfair” and “the worst politicization of justice in our country.”

The White House strongly denied any political interference, but the unprecedented special counsel investigation of a former president – and current presidential candidate – sets the stage for a drawn-out legal battle.

At a press conference, Attorney General Merrick Garland announced the appointment of Jack Smith, until recently a chief prosecutor in The Hague charged with probing Kosovo war crimes, to take over the two ongoing federal probes into Trump.

One is focused on the former president’s efforts to overturn the results of the 2020 election and the January 6, 2021, attack on the US Capitol by his supporters.

The other is an investigation into a cache of classified government documents seized in an FBI raid on Trump’s Mar-a-Lago residence in Florida in August.

Garland said naming a special counsel was in the public interest because both the Republican Trump and his Democratic successor Joe Biden have stated their intention to run in 2024, although only Trump has officially declared for now.

“Appointing a special counsel at this time is the right thing to do,” Garland said. “The extraordinary circumstances presented here demand it.”

At the White House, Press Secretary Karine Jean-Pierre said Biden had no advance notice of Garland’s plans to name a special counsel.

- ‘So unfair’ -

Trump claimed in an interview with Fox News Digital that he was being targeted by the Biden administration to prevent him winning back the presidency.

“This is a disgrace and only happening because I am leading in every poll in both parties,” he said. “It is not acceptable. It is so unfair. It is so political.”

“This will not be a fair investigation,” Trump told guests later at his Mar-a-Lago home.

“The horrendous abuse of power is the latest in a long series of witch hunts,” he said, to applause.

In a statement, Smith, who previously headed the Justice Department’s Public Integrity section, said the “pace of the investigations will not pause or flag under my watch.”

“I will exercise independent judgement and will move the investigations forward expeditiously and thoroughly to whatever outcome the facts and the law dictate,” he said.

Trump’s entry into the White House race on Tuesday makes indicting him a much more delicate matter.

The appointment of an independent prosecutor to oversee the twin investigations could serve to help insulate Garland, a Biden appointee, from charges that the probe is politically motivated.

The special counsel will determine whether the former president should face any charges but the attorney general will have the ultimate say on whether charges should be filed.

Even if charged, the 76-year-old Trump can still run for president – nothing in US law bars a person charged with or convicted of a crime from doing so.

While in office, Trump was investigated by special counsel Robert Mueller over obstruction of justice and possible 2016 election collusion with Russia, but no charges were brought against him.

- Other legal woes -

In addition to the federal investigations, Trump faces other legal woes.

New York state’s attorney general Letitia James has filed a civil suit against Trump and three of his children, accusing them of business fraud.

And Trump is being investigated for pressuring officials in the southern swing state of Georgia to overturn Biden’s 2020 victory – including a now-infamous taped phone call in which he asked the secretary of state to “find” enough votes to reverse the result.

Trump’s unusually early announcement that he was running for president in 2024 was seen by some analysts in Washington as an attempt to stave off potential criminal charges.

Trump was impeached by the Democratic-majority House of Representatives in 2019 for seeking political dirt on Biden from Ukraine, and again after the January 6 attack on the Capitol, but was acquitted by the Senate both times.