The Panama legal firm at the heart of a massive data leak kept clients who were subject to international sanctions, documents show.
Mossack Fonseca worked with 33 individuals or companies who have been placed under sanctions by the US Treasury, including companies based in Iran, Zimbabwe and North Korea.
One had links to North Korea's nuclear weapons programme.
Mossack Fonseca registers companies as offshore entities operated under its own name.
This meant the identities of the real owners were hard to trace because they were kept out of public documents.