Close aides of Russian president Vladimir Putin are among those whose assets feature in a vast expose of tax havens published after a year-long investigation into 11.5 million leaked documents.

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 Mr Putin's name is not mentioned in the documents, his close associates "secretly shuffled as much as $2bn 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.

Documents linking an Irish-registered company with an address in Drumcondra, Dublin, to arms and other deals feature in the leaked material, according to the Irish Times.

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

Reacting to the publication of the papers, Oxfam Ireland Chief Executive Jim Clarken said: "This exposé offers a rare glimpse into the murky practices of tax dodging - and the sheer size and scale revealed is staggering.

"As long as tax dodging continues to drain government coffers the world over, there is a human cost with less to spend on vital public services and the resources needed to tackle poverty, put children in school and prevent citizens dying from lack of healthcare."

The 11.5 million documents involved in this leak make it larger than the US diplomatic cables released by WikiLeaks in 2010, and the intelligence documents given to journalists by Edward Snowden in 2013.