Switzerland has frozen $900 million held in accounts belonging to a top Angolan businessman as part of a money-laundering investigation, according to court documents seen by Reuters, one of the largest personal asset freezes in Swiss history.

Carlos Manuel de São Vicente was a key figure in Angola’s oil industry, heading a group of companies which sold insurance and reinsurance contracts to state oil company Sonangol.Prosecutors said they froze $1.25 billion in accounts associated with de São Vicente, his family and companies late last year after Swiss banks flagged transfers to them as suspicious. They released most of the accounts in April 2019, save for two, which were in de São Vicente’s name.

“The public prosecutor opened, on December 4, 2018, a criminal procedure for money laundering against (Carlos Manuel de São Vicente) and also ordered the same day the freezing, with a view toward confiscation or of restitution to any injured parties,” of targeted bank accounts, according to the document.

The existence of the case was first reported by Swiss judicial blog Gotham City.

Angola-based De São Vicente, the court documents say, described the transfers between 2012 to 2019 as legitimate reimbursement for loans he had paid earlier and had appealed against the freeze.

“My client strongly refutes the charges against himself,” Clara Poglia of the Geneva-based law firm Schellenberg Wittmer Ltd. representing De São Vicente told Reuters in a statement.

“He confirms that he has always acted according to the law as it will be demonstrated in the frame of the criminal proceedings,” she added.

The appeal to have the two accounts unblocked was rejected by the Geneva court on July 9. Switzerland’s federal tribunal told Reuters on Wednesday that they had yet to receive a fresh appeal from de São Vicente in relation to the frozen funds, for which he is eligible until a deadline later this month.

De São Vicente’s wife, whose name along with those of other family members are attached to bank accounts originally blocked and then released by the Swiss prosecutors, is Irene Neto, a former deputy minister from Angola’s ruling party and daughter of Angola’s former president.

An Angolan political foundation headed by Neto did not immediately respond to a Reuters request for comment.

CORRUPTION PROBES

Swiss prosecutors allege that under de São Vicente’s leadership the AAA Seguros company held a monopoly over insurance and reinsurance of the country’s state-run oil industry between 2000 and 2016.

A presidential decree in 2016 revoked AAA’s insurance role over the oil industry citing its “allegedly non-transparent management” and the company’s authorization to operate in Angola was revoked earlier this year and it was dissolved.

Sonangol did not immediately respond to a Reuters request for comment.

Angola, which draws a third of state revenues from oil, is seeking to defy decades of perceived corruption and nepotism as it seeks to attract foreign investment to its flagging economy.

Despite being rich in diamonds and Africa’s number two oil exporter, Angola’s debt to GDP ratio is expected to hit 132% this year, according to the IMF. Earlier this year it said it was seeking other countries’ help to recover state funds lost because of corruption.

Prosecutors in Angola launched a corruption probe late in 2019 into Isabel Dos Santos, daughter of another ex-president, alleging that she improperly profited from her chairmanship of Sonangol from 2016 to 2017.

Her brother Jose Filomeno de dos Santos, the former head of Angola’s $5 billion sovereign wealth fund, was found guilty by an Angolan court this year of an illegal money transfer to a London bank. The Dos Santos family denies the charges.