A grand jury indictment charged Tan Wee Beng, 41, with working with several other unnamed actors to move money through the international banking system for North Korean banks between 2011 and 2018, violating international sanctions on North Korea.

Separately, the US Treasury slapped sanctions on Tan and two companies he ran -- Wee Tiong(S) Pte and WT Marine Pte, both of which did business with North Korea.

Tan "conducted illicit transactions totaling millions of dollars in support of North Korean entities in blatant violation of a host of economic sanctions the United States has established against North Korea and North Korean entities," said FBI assistant director William Sweeney in a statement.

The indictment and sanctions announcements said one of Tan's companies handled millions of dollars worth of commodity contracts for Pyongyang, and said Tan followed instructions from sanctioned North Korean banks on how to move funds for them through the global banking system.

Money transfers involved front companies in Singapore, Thailand, Hong Kong and elsewhere, they said.

They also said that ships operated by Tan's WT Marine engaged in sanctions-violating activities involving North Korea.

The FBI placed Tan on its "most wanted" list, saying his whereabouts are currently unknown.

According to a 2015 article in the Singapore Straits Times and other public records, Tan was an up-and-coming businessman, the heir to his father's commodities trading business, which had hundreds of millions of dollars in annual revenues.

In 2011, the year US authorities say he began laundering money for North Korea, he was named an "entrepreneur of the year" by Ernst and Young, the global business consultancy.