A United Nations panel has accused North Korea of continuing to export nuclear and missile technology in defiance of a UN ban.
The experts said North Korea has used front companies and intermediaries to sell weapons and provide illegal assistance to Iran, Syria and Burma.
The preliminary report was compiled by a seven-member group that monitors Pyongyang's compliance with sanctions.
The panel has called for further, urgent investigations.
The 47-page report outlined a broad range of techniques used by North Korea to evade sanctions imposed by the UN after the North's nuclear tests of 2006 and 2009, the Associated Press reports.
The report said North Korea had moved quickly to replace banned individuals and entities with others to enable it to continue the nuclear trade.
Among a number of "masking techniques", it said the North describes exports falsely, mislabels shipping container contents, falsifies information about the destinations of goods and uses "multiple layers of intermediaries, shell companies, and financial institutions".
The report said North Korea has a range of legitimate trade offices but also sustains links with international criminal organisations to pursue the banned trades.
An unnamed diplomat told Reuters the findings were "not entirely surprising".
"The point is that North Korea has been providing that kind of aid to Iran, Syria and Burma," he said.
The report comes before a crucial day of talks in New York about the future of the Nuclear Non-Proliferation Treaty.
It also comes at a time of increased tension surrounding what international investigators say was a deadly North Korean torpedo attack on a South Korean warship in March.