Spain, France and Australia have announced probes into tax evasion and money laundering following the release of the so-called Panama Papers.
Millions of documents leaked to a number of media organisations across Europe apparently show the ways the rich and famous can exploit secretive offshore tax regimes.
Many former and current world leaders are reportedly implicated in the documents leaked from offshore law firm Mossack Fonseca.
People in Reykjavik protest against the Icelandic PM
Among the revelations is a network of secret deals and loans worth bn (£1.4bn) which apparently leads to Russian President Vladimir Putin.
Others said to be involved in the schemes include the prime ministers of Iceland and Argentina, as well as footballer Lionel Messi – among those now being investigated by Spanish authorities.
In the UK, HMRC has asked the International Consortium of Investigative Journalists (ICIJ) for access to the data and promised to “act on it swiftly and appropriately” if there is any wrongdoing.
The US Justice Department also said it was reviewing the documents.
Around 370 reporters from 100 media organisations spent a year analysing and verifying the millions of documents.
As the fallout from the leak spreads, French ministers said they would claw back any money if the allegations are proven.
Michel Sapin, the country’s finance minister, warned of “penalties” for anyone found to have dodged tax through shell companies or unregistered accounts.
He also said Panama, in central America, had been under surveillance for some time.
Spain, too, has taken swift action and opened a money laundering probe.
Barcelona footballer Lionel Messi – due to stand trial on separate tax evasion charges in May – has denied allegations he is involved in shielding money via a Panama firm.
The star and his father are allegedly named in the papers as the owners of Mega Star Enterprises, a company not previously disclosed to Spanish authorities.
“The Messi family wants to make clear that Lionel Messi has not carried out any of the acts attributed to him, and accusations he created a … tax evasion plot, including a network of money-laundering, are false and insulting,” said a statement.
The Australian Tax Office also announced it had started an investigation into 800 of its citizens named among the 11.5 million records.
Law firm Mossack Fonseca was already being probed in Germany and Brazil, where it is part of a major money laundering probe that has rocked the government.
Holding money in offshore companies can be for entirely legitimate reasons and the firm denies any wrongdoing, saying it has robust due diligence procedures.
Russia’s Kremlin has called suggestions that President Vladimir Putin is associated with the scandal as “nothing concrete and nothing new”.
Mr. Putin’s friends are reportedly named in the documents, but his spokesman denied he was implicated and said he was the target of a smear campaign.
“This Putinophobia abroad has reached such a point that it is in fact taboo to say something good about Russia, or about any actions by Russia or any Russian achievements,” said Mr Putin’s spokesman Dmitry Peskov.
“But it’s a must to say bad things, a lot of bad things, and when there’s nothing to say, it must be concocted.”
Iceland’s Prime Minister is also feeling the heat, walking out of an interview on Monday while thousands of protesters gathered outside the country’s parliament.
The Panama Papers are said to show Sigmundur David Gunnlaugsson and his wife owned a company in the British Virgin Islands which held £2.8m of investments in the country’s collapsed banks.
Mr. Gunnlaugsson has ruled out resigning and denied there had been a conflict of interest.
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