One of the largest data leaks in history reveals how world leaders and aides hide their cash

A year-long investigation just revealed where 140 political figures - including 12 current of former heads of states - hide their cash.

In what is potentially one of the largest data dumps in history, over 11 million documents held by the Panama-based law firm Mossack Fonseca was leaked to German newspaper Suddeutsche Zeitung. In turn, the paper shared the information with the International Consortium of Investigative Journalists (ICIJ) - which is made up of 107 media organisations in 78 countries.

The BBC said it also analysed the document but it "doesn't know the identity of the source."

Close aides of Russian president Vladimir Putin are among those whose assets feature in a vast expose of tax havens published Sunday.

The assets of around 140 political figures -- including 12 current of former heads of states -- are mentioned in the revelations, according to the probe by the International Consortium of Investigative Journalists (ICIJ) and German daily Sueddeutsche Zeitung.

The investigation yielded 11.5 million documents from around 214,000 offshore entities, the ICIJ said on its website.

The leaked data from 1975 to the end of last year provides what the ICIJ described as a "never-before-seen view inside the offshore world."

Names figuring in the leak included the president of Ukraine, the king of Saudi Arabia and the prime ministers of Iceland and Pakistan, the ICIJ statement said.

Although Putin's name is not mentioned in the documents, his close associates "secretly shuffled as much as $2 billion through banks and shadow companies," the ICIJ said.

"These findings show how deeply ingrained harmful practices and criminality are in the offshore world," said Gabriel Zucman, an economist at the US-based University of California, Berkeley, cited by the consortium.

The leaked documents came from Mossack Fonseca, a law firm with offices in more than 35 countries. They were reviewed by a team of more than 370 reporters from over 70 countries, according to the ICIJ.

The BBC cited Panama-based Mossack Fonseca as saying it had operated "beyond reproach" for 40 years and had never been charged with any criminal wrongdoing.

It wasn't clear who was the original source of the leaked documents.