Documents leaked from an offshore law firm show a Japanese hospital and a doctor profited from unlisted shares in a Singapore medical firm, with the doctor profiting ¥100 million ($880,000) despite the hospital's involvement in clinical trials for the company.

According to an analysis of the documents known as the "Paradise Papers," doctors in the United States and India also bought unlisted shares in Biosensors International Group Ltd., a medical device company specializing in cardiovascular treatment. The firm was incorporated in Bermuda, a British island territory known as a tax haven.

The hospital, Sendai Kousei Hospital in Miyagi Prefecture, and the doctors in question have admitted to buying the shares, but denied their conduct constituted a conflict of interest or affected any of their decisions regarding medical treatment.