The head of a Panama-based law firm at the centre of a massive leak of offshore financial data on Sunday denied any wrongdoing, and said his firm has fallen victim to “an international campaign against privacy".

German newspaper Suddeutsche Zeitung said it received a cache of 11.5 million leaked documents from the law firm's database, and shared them with more than 100 other international news outlets as well as the International Consortium of Investigative Journalists (ICIJ).

Ramon Fonseca, the director of Panama-based law firm Mossack Fonseca, specialised in setting up offshore companies, said in a telephone interview with Reuters that his firm had suffered a successful but “limited” hack.

Fonseca, the firm's co-founder and until March a senior government official in Panama, said his firm has formed more than 240,000 companies, adding that the “vast majority” have been used for “legitimate purposes.”

The ICIJ report published on Sunday details billions of dollars of shadowy financial transactions moved through numerous offshore accounts.

Britain’s Guardian newspaper said the documents showed a network of secret offshore deals and loans worth $2 billion led to close friends of Russian President Vladimir Putin. Reuters couldn't independently confirm those details.

Fonseca emphasised that the firm is not responsible for the activities of the companies it incorporates.

“We're dedicated to making legal structures which we sell to intermediaries such as banks, lawyers, accountants and trusts, and they have their end-customers that we don't know,” said Fonseca.

He said all of the firm's clients have been notified of "this problem,” arguing that the firm has been caught up in an international anti-privacy campaign.

“We believe there's an international campaign against privacy. Privacy is a sacred human right (but) there are people in the world who do not understand that and we definitely believe in privacy and will continue working so that legal privacy can work,” he said.

The law firm said in a separate statement published by the Guardian : “It appears that you have had unauthorised access to proprietary documents and information taken from our company and have presented and interpreted them out of context.”

Panama's government said in a statement on Sunday that it will cooperate with any eventual judicial proceeding relating to the allegations in the report.

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