The leak, which came to light on Sunday with the participation of the Washington-based International Consortium of Investigative Journalists, suggests that 140 politicians and officials from around the globe, including 72 former and current world leaders, have connections with the secret companies to escape tax scrutiny in their countries.
The leak involves 11.5 million documents from one of the world's largest offshore law firms, Mossack Fonseca, and implicates Russian President Vladimir Putin with secret offshore financial deals to channel and launder money.
Among the other politicians implicated in the leak are Pakistani Prime Minister Nawaz Sharif, former Egyptian President Hosni Mubarak, former Libyan leader Muammar Gaddafi, Syrian President Bashar al-Assad and many others.
According to the ICIJ, which published details of the extensive investigation on its web page, the leak includes documents generated over almost 40 years by the large Panamanian law firm Mossack Fonseca, which specialises in capital and asset management.
The documents mention more than 214,000 offshore companies in more than 200 countries and territories.
It is the largest journalistic leak in history, containing significantly more information than was divulged by WikiLeaks in its publication of secret US diplomatic cables.
The investigation into the documents was undertaken over the course of the past year and headed by German daily Suddeutsche Zeitung and the ICIJ, with the collaboration of reporters from more than 100 media outlets in 78 countries around the world.
The documents reveal the creation of thousands of offshore companies and tax havens to allow politicians, celebrities and other well-known people to secretly manage their assets.
Although owning an offshore company is generally not illegal, it is a business structure that is often used for illegal dealings.
Mossack Fonseca on Sunday denied, when queried by EFE, any link with any crimes allegedly committed by hundreds of its clients.
The investigation dubbed The Panama Papers reveals that Putin secretly has a personal fortune of up to $A2.61 billion ($US2 billion) managed through banks and shadow corporations.
Other documents show that Chinese President Xi Jinping, Ukrainian President Petro Poroshenko, Icelandic Prime Minister Sigmundur David Gunnlaugsson and the deceased father of British Prime Minister David Cameron all have had assets managed by offshore companies.
Also having assets managed through undeclared corporations in The Bahamas was Argentine President Mauricio Macri when he was mayor of Buenos Aires, as well as soccer great Lionel Messi, also from Argentina, the investigation contends.
Among the Spaniards implicated in the documents are Pilar de Borbon, the sister of former King Juan Carlos, and film director Pedro Almodovar.
The ICIJ says that the investigation found evidence against at least 33 people and companies being scrutinised by the US government for evidence of participating in illicit activities with Mexican drug traffickers, terrorist organisations like Hezbollah and nations such as Iran and North Korea.
