Grand jury convened to consider criminal charges against Donald Trump

One of the most powerful prosecutors in the US has begun a hearing to decide whether to charge former president Donald Trump.

Manhattan district attorney (DA) Cyrus Vance has convened a grand jury, who will decide whether to indict Mr Trump on as-yet unknown charges.

A grand jury proceeding has a similar function to a committal hearing in Australia. The select group will meet and hear evidence, and decide whether a criminal trial is warranted.

READ MORE: What does a new criminal inquiry mean for Donald Trump?

The Washington Post reports the grand jury panel has already convened and is anticipated to sit three days a week for six months.

Mr Vance or the district attorney's office have not spoken about the grand jury proceedings, which are kept secret.

But the anticipated lengthy nature of the proceedings offer some indication the criminal case against Mr Trump is expansive and complex.

Mr Trump lashed out against the grand jury proceedings.

"This is a continuation of the greatest Witch Hunt in American history," he wrote on his blog.

"This is purely political, and an affront to the almost 75 million voters who supported me in the Presidential Election, and it's being driven by highly partisan Democrat prosecutors.

"New York City and State are suffering the highest crime rates in their history, and instead of going after murderers, drug dealers, human traffickers, and others, they come after Donald Trump."

READ MORE: Trump Organisation now under criminal investigation in New York

The Post reports the Manhattan DA is scrutinising whether the value of Trump Organisation properties were manipulated to defraud banks, insurance companies or tax authorities.

The investigation began with Mr Trump's former personal lawyer Michael Cohen, who is now cooperating with the DA's office.

Mr Trump is also facing a separate criminal investigation from the New York Attorney-General's office.

Mr Trump has not been criminally charged.