A massive leak of 11.5 million tax documents has exposed the secret offshore dealings of aides to Russian president Vladimir Putin, world leaders and celebrities including Barcelona forward Lionel Messi.

Paris: A massive leak of 11.5 million tax documents has exposed the secret offshore dealings of aides to Russian president Vladimir Putin, world leaders and celebrities including Barcelona forward Lionel Messi.

An investigation into the documents by more than 100 media groups, described as one of the largest such probes in history, revealed the hidden offshore dealings in the assets of around 140 political figures.

The vast stash of records was obtained from an anonymous source by German daily Sueddeutsche Zeitung and shared with media worldwide by the International Consortium of Investigative Journalists (ICIJ).

The documents, from around 214,000 offshore entities covering almost 40 years, came from Mossack Fonseca, a Panama-based law firm with offices in more than 35 countries.

The investigations allege close associates of Putin, who is not himself named in the documents, "secretly shuffled as much as $2 billion through banks and shadow companies".

Twelve current or former heads of state are named in the investigations, including the prime ministers of Iceland and Pakistan, the president of Ukraine and the king of Saudi Arabia, as well as sporting and movie stars including Jackie Chan.

They allege Chinese President Xi Jinping and his family have links to offshore accounts, and claim Iceland's prime minister secretly owned millions of dollars of bank bonds during the financial crisis.

Xi has led a high-profile anti-graft drive in China, targeting the excessive wealth accumulated by Communist Party cadres.

The papers also cast fresh light on the corruption scandal engulfing football's world governing body, revealing that Fifa ethics committee member Juan Pedro Damiani had business ties with three men who have been indicted over the probe.

Disgraced Uefa chief Michel Platini allegedly used Mossack Fonseca to administer an offshore company, while Messi and his father apparently own a shell company not discovered in a Spanish investigation into the football star's tax affairs.

Platini's communications service said in a statement sent to AFP that "all of his accounts and assets are known to the tax authorities in Switzerland, where he has been a tax resident since 2007".

'Attack on Panama'

"I think the leak will prove to be probably the biggest blow the offshore world has ever taken because of the extent of the documents," said ICIJ director Gerard Ryle.

One of the law firm's founders, Ramon Fonseca, told AFP the leaks were "a crime, a felony" and "an attack on Panama".

"Certain countries don't like it that we are so competitive in attracting companies," he said.

Panama's government said it had "zero tolerance" for any shady deals, and vowed to "vigorously cooperate" with any legal investigations.

Though most of the alleged dealings are said by the ICIJ to be legal, they are likely to have a serious political impact on many of those named.

Iceland's Prime Minister Sigmundur David Gunnlaugsson is expected to face a no-confidence vote this week over allegations he used a secret offshore firm called Wintris Inc. to hide millions of dollars in the British Virgin Islands.

"I have never hidden assets," Gunnlaugsson told a journalist from the Swedish SVT channel. "It's a bit like you're accusing me of something," he added, visibly irritated, before calling off the interview.

His spokesman insisted he and his wife have scrupulously followed the law.

At least 33 people and companies listed in the documents were blacklisted by the US government for wrongdoing, including dealings with North Korea and Iran, as well as Lebanon's Islamist group Hezbollah, the ICIJ said.

The leaked data, covering 1977 to the end of last year, provides what the ICIJ described as a "never-before-seen view inside the offshore world".

The massive leak of documents recalls Wikileaks' exploits of 2010 — which included the release of 500,000 secret military files on the wars in Afghanistan and Iraq and 250,000 diplomatic cables, and infuriated the US.

'Biggest leak in history'

However, in terms of size, "the 'Panama Papers' is likely the biggest leak of inside information in history," according to ICIJ.

"It is equally likely to be one of the most explosive in the nature of its revelations," the group added.

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

The documents show that "banks, law firms and other offshore players often fail to follow legal requirements to make sure clients are not involved in criminal enterprises, tax dodging or political corruption," the ICIJ said on its website.

"The files show that these fixers and middlemen protect themselves and their clients by concealing suspect transactions. In some instances, they work to head off official investigations by backdating and destroying documents," it added.

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

The leaked documents were reviewed by a team of more than 370 reporters from over 70 countries, according to the ICIJ.

It was not immediately clear who was the original source of the leaked documents.