Sassou Nguesso is being investigated for the alleged embezzlement of several million dollars.
The family of the president of the Republic of Congo is also the subject of an investigation into its involvement in France in the so-called "ill-gotten gains" affair.
Prosecutors in the US are investigating the son of the president of the Republic of Congo for the alleged embezzlement of several million dollars from the coffers of the publicly-owned National Society of Petroleum of Congo (SNPC), according to the NGO Global Witness.
In Miami, US federal prosecutors "have made arrangements to seize" a luxurious property belonging to Denis Christel Sassou Nguesso, the NGO added in a document.
Global Witness was able to consult the request of American prosecutors dated June 12, and share it with media including AFP.
Sassou Nguesso bought this 3,500 m2 penthouse, put up for sale at $2.4 million "with funds he diverted from the SNPC", according to this document, which traces the route of alleged money laundering.
In 2010, the younger Sassou Nguesso "was appointed by his father (also Sassou Nguesso) as deputy managing director" of the SNPC.
"That position gave him enormous control over SNPC's activities and, critically, its finances.
"Between 2011 and 2014", the younger Sassou Nguesso "embezzled millions of dollars from the SNPC", the American judicial document continues.
The funds are deemed to have passed through the accounts of shell companies housed in a subsidiary of the Gabonese bank BGFI-Bank.
"Between April 30, 2009 and April 22, 2016, Minister Nguesso transferred approximatively $10.3 million to bank accounts," opened by an associate in Florida.
According to the American public prosecutor, this partner is a "US resident" and "son of an ex-official of the Gabonese government".
The partner allegedly "used the stolen funds to acquire real estate and luxury items" for Sassou Nguesso (son) and his relatives, "including the Miami property".
Brazzaville has so far offered "no reaction" to the dissemination of this document, a source within the presidency told AFP.
The family of President Sassou Nguesso is also the subject of an investigation into its involvement in France in the so-called "ill-gotten gains" affair.
On his Facebook page, Denis Christel Sassou Nguesso, 45, describes himself as "philanthropist" and member of the national assembly for the town of Oyo -- his father's hometown -- after having "officiated in the world of oil".
His father, 76, first took the presidency in 1979, staying in power until 1992. He returned to the presidency in 1997 and has held the top job ever since.
In 2019, San Marino authorities seized a bank account containing approximately 19 million euros allegedly deposited by President Nguesso.
He is a candidate for reelection in the presidential election in March 2021.