Former US President Donald Trump's company and its finance chief have been indicted in an investigation into alleged tax crimes, US media report.

Allen Weisselberg, 73, turned himself in to authorities in New York on Thursday morning, ahead of the expected unsealing of as-yet-unknown charges.

"Mr Weisselberg intends to plead not guilty and he will fight these charges in court," his lawyers said.

Mr Trump is not expected to be implicated personally in the case.

New York City has already cut business ties with the twice-impeached former president.

The Trump Organization is a family holding company that owns hotels, golf clubs and other properties.

Any criminal charges brought against it would mark the first in long-running investigations on alleged fraud by both the Manhattan district attorney and the state attorney general.

Charges by District Attorney Cyrus Vance are expected to focus on whether Mr Weisselberg and other company executives received benefits such as apartment rentals or leased cars without reporting them properly on their tax returns.

Mr Weisselberg entered Manhattan's criminal court building early on Thursday, the New York Times said. He and at least one other Trump Organization representative are expected to appear in court later in the day.

Mr Trump and his allies have said the investigations are politically motivated.

In a statement, the Trump Organization said Mr Vance was using Mr Weisselberg, who has worked for Trump's business for nearly 50 years, "as a pawn in a scorched earth attempt to harm the former president."

"This is not justice; this is politics," the company said.

If the company is found guilty, however, certain business partners might draw a line under their relationship with the Trump Organization and the company could face fines.

New York City, for example, has already announced it will terminate contracts with the firm to run skating rinks, a carousel and a golf course, in the aftermath of the US Capitol riots.

Daniel Goldman, who was lead lawyer in the US House of Representatives for the first impeachment of Mr Trump in 2019, tweeted that the indictment could spur lenders to call in their loans, driving the Trump Organization to bankruptcy.

The investigations will also take into account eight years of Mr Trump's personal and corporate tax returns, obtained by prosecutors after a long legal battle, which ended in the Supreme Court in February.

Mr Trump, who inherited money from his father and went on to become a property developer, is the first president since Gerald Ford in the 1970s not to have made his tax returns public.

Despite facing a number of investigations, the former president has denied any wrongdoing personally or in his business.