Congo President Joseph Kabila and his family own stakes in more than 80 companies at home and abroad that are likely worth 10s of millions of dollars, a report by a U.S.-based body said on Thursday.

The report by the Congo Research Group at New York University is based almost entirely on public records like land titles and incorporation documents. It is the most comprehensive mapping to date of Kabila and his family's fortune after two decades in charge of Africa's top copper producer.

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Reuters was not immediately able to independently confirm the information in the report, which does not allege wrongdoing by Kabila. The president is barred by Democratic Republic of Congo's constitution from being involved in a professional activity but not from owning companies or making investments.

"No one is barred from having assets because he is from the Kabila family," government spokesman Lambert Mende told Reuters.

"If someone thinks that (Kabila) committed an objectionable act related to those assets, (that person) can address the justice system."

Before Kabila's father, Laurent-Desire, came to power in 1997, he and his family lived in exile in Tanzania, where, according to the report and other accounts, the family struggled financially.

Now, the Kabila family's holdings include over 70,000 hectares of farmland, a lucrative stake in Congo's largest mobile phone network and over 100 mining permits for diamonds and gold, the report said.

"A conservative reading of public documents suggests that their companies have had hundreds of millions of dollars in revenues since 2003, and that they own assets that are easily worth many tens of millions of dollars," the report said.

Kabila, who succeeded his assassinated father in 2001, refused to step down when his mandate expired last December, citing budgetary constraints and delays enrolling voters for an election to replace him.

Congo Research Group is a non-profit body directed by Jason Stearns, a former U.N. investigator in Congo and author of a well-known book about Congo's civil wars.