Leaked documents, known as the Paradise Papers, show a former Kazakhstan official, who was convicted of embezzling $US20 million, was a beneficiary of family trusts listed in the Cook Islands.
The papers have have been shining a light on the investment practices of the rich and powerful using offshore tax havens.
They include more than half a million documents (556,000) from the Singapore-based trust specialist Asiaciti, which has branches in the Cook Islands and Samoa.
The International Consortium of Investigative Journalists which has been studying the papers reports the family of Serik Burkitbayev set up three trusts in the Cook Islands in September 2012.
Burkitbayev was a former aide to the Kazakhstan President Nursultan Nazarbayev and head of Kazakhstan's state-owned oil and gas company.
He was jailed after being convicted of embezzlement and other crime in 2009.
Emails sent in 2013 reportedly show Asiaciti knew of Burkitbayev's political past, but proceeded with the family's business.
The consortium reports Asiaciti reviewed the documents and said it was "comfortable" proceeding with the trusts which were closed in 2016.
Asiaciti said it complies with applicable laws and regulations at all times.
