Ukraine has announced it is reviewing the closure of criminal investigations concerning a gas company which employed former US vice president Joe Biden’s son Hunter.

The probes involved allegations of tax offences, illegal enrichment and illegal distribution of drilling licences made against Burisma Holdings and its founder Mykola Zlochevsky. They were closed following a court order in 2016.

Announcing the review in a press conference on Friday, Ukraine’s new chief prosecutor Ruslan Riaboshapka said he had launched an audit into approximately 15 historic cases that may have been closed improperly.

President Donald Trump and his associates have claimed that Biden Snr, then vice president with responsibility for Ukraine, shut down the investigations by forcing the resignation of Viktor Shokin, the former general prosecutor.

There is no evidence to support these claims. Paper trails and the testimony of those involved in the case at the time suggest that, on the contrary, Mr Shokin stood in the way of any investigation into Burisma. There were no active investigations at the time of the former chief prosecutor’s departure in 2016.

But these discredited claims now lie at the heart of a US congress impeachment inquiry into possible abuse of power by the US president.

The inquiry was set up in late September, following a whistleblower complaint that Mr Trump tried to strong-arm his Ukrainian counterpart, Volodymyr Zelensky, into announcing an investigation against Hunter and Joe Biden. On Thursday evening, that inquiry released numerous text messages that appeared to document how State Department officials coordinated with Ukraine to secure such an investigation.

Prosecutor Riaboshapka’s Friday announcement gave an impression of handing the Trump administration part of what it demanded. But it also stopped short of offering a full investigation into the company or either of the Bidens. The new chief prosecutor also said he had seen no evidence of wrongdoing by the former vice president’s son.

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“We are conducting an audit of historic cases carried out by the Prosecutor General. ... There are about 15 such cases,” he said. Mr Riaboshapka said his review had nothing to do with the scandal in Washington, saying that his office was “outside of politics”.

While the move was initially interpreted in as an overture to Mr Trump’s entreaties to investigate, legal experts said it did not necessarily represent a shift in position by Ukrainian authorities.

Posting on Twitter, the anti-corruption campaigner Daria Kaleniuk said the review was happening ahead of a planned reform, due next month, which will see investigative powers removed from the Prosecutor General’s office.