PARIS (AFP) - A massive leak of 11.5 million tax documents on Sunday (April 3) exposed the secret offshore dealings of several world leaders, celebrities and their friends and family members. Those implicated in the leak include the families of Chinese President Xi Jinping, Malaysian Prime Minister Najib Razak and Barcelona forward Lionel Messi, as well as film star Jackie Chan and close aides of Russian President Vladimir Putin.

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 - including 12 current or former heads of states.

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 investigation yielded 11.5 million documents from around 214,000 offshore entities, the ICIJ said. The leaked documents came from Mossack Fonseca, a Panama-based law firm with offices in more than 35 countries.

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.

Among the main claims of the ICIJ investigations:

- The files identified offshore companies linked to the family of Chinese President Xi Jinping, who has led a tough anti-corruption campaign in his country, the ICIJ said.

- They also alleged that the son of Malaysian Prime Minister Najib Razak assumed the directorship of two offshore companies while his father was in power.

- Argentine football great Messi and his father owned a Panama company, Mega Star Enterprises Inc, a shell company that had previously not come up in Spanish investigations into the father and son's tax affairs.

- The files also identify a convicted money launderer who claimed he'd arranged a US$50,000 illegal campaign contribution used to pay the Watergate burglars, 29 billionaires from Forbes' rich list, and martial arts film star Jackie Chan.

- The late father of British Prime Minister David Cameron also allegedly played an instrumental role in creating and developing an offshore investment firm that managed to avoid taxes.

- Close associates of Mr Putin, who is not himself named in the documents, "secretly shuffled as much as US$2 billion (S$2.7 billion) through banks and shadow companies", the ICIJ said.

- In Iceland, the files allegedly show Prime Minister Sigmundur David Gunnlaugsson and his wife secretly owned an offshore firm holding millions of dollars in Icelandic bank bonds during the country's financial crisis.

- The law firm of a member of Fifa's ethics committee, Juan Pedro Damiani, had business ties with three men indicted in the Fifa scandal: former Fifa vice-president Eugenio Figueredo, as well as Hugo Jinkis and his son Mariano who were accused of paying bribes to win soccer broadcast rights in Latin America.

Also in the world of football, Francetvinfo named Uefa president Michel Platini as the beneficiary of a Panama-based tax company, adding however that no illegal activity was alleged.

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".

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

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 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.

"These findings show how deeply ingrained harmful practices and criminality are in the offshore world," said Mr Gabriel Zucman, an economist at the US-based 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.

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

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

Panama's government vowed Sunday to "vigorously cooperate" with any legal probe that might be launched in the wake of the "Panama Papers" data leak.

"The Panamanian government will vigorously cooperate with any request or assistance necessary in the event of any legal action occurring," it said in a statement.