According to the International Consortium of Investigative Journalists, leaked documents from the US Treasury Department reveal that major global banks have been doing business with high-risk customers for years.

The ICIJ, which analysed the files, said five global banks had "defied money laundering crackdowns by moving staggering sums of illicit cash for shadowy characters and criminal networks."

The banks were reluctant to report such suspicious transactions to authorities and sometimes did so with a delay of years, according to the report.

The trove of more than 2000 "suspicious activity reports" were issued by banks and submitted to US authorities in the period 2000 to 2017.

It has been dubbed the FinCEN Files, after the US Treasury's Financial Crimes Investigation Network. The documents reportedly cover transactions worth a total of 2 trillion dollars.

The ICIJ said the research was the result of a joint investigation by 110 media outlets in 88 countries.

The US media outlet Buzzfeed News received the leaked documents and shared them with the journalist network, thus enabling the research.

Germany's Netzwerk Steuergerechtigkeit, an organisation that has been pointing out shortcomings in the fight against international money laundering for years, said it was not surprised by the revelations.

However, the leak did give "a shocking insight into the central role of the US financial system as the engine room of global money laundering," Markus Meinzer from the network said.

"If organised crime infiltrates the economy and kleptocrats plunder their states with the help of Western banks, freedom and democracy are threatened everywhere. The constitutional state must finally take money laundering seriously and punish it seriously," Meinzer said.

Deutsche Bank and HSBC, two of the banks named by the researchers, both said the cases noted in the reports were "historical" in nature.

Germany's biggest bank said regulators were aware of the issues and that they had been investigated and that agreements had been reached with the authorities.

"Where necessary and appropriate, consequence management was applied," the bank said in a statement. "At Deutsche Bank we have devoted significant resources to strengthening our controls and we are very focused on meeting our responsibilities and obligations."

A spokesman at HSBC, Britain's largest bank, said the bank was "a much safer institution than it was in 2012" following efforts to improve its "ability to combat financial crime across more than 60 jurisdictions."

Australian Associated Press