An award-winning investigative team published a trove of files Sunday allegedly showing how Africa's richest woman syphoned hundreds of millions of dollars of public money into offshore accounts.

The New York-based International Consortium of Investigative Journalists (ICIJ) worked with newspapers such as Munich's Suddeutsche Zeitung to reveal the "Panama Papers" tax haven scandal in 2016.

Its latest series called "Luanda Leaks" zeros in on Isabel dos Santos, the daughter of former Angola president Jose Eduardo dos Santos.

Angola's prosecutors last month froze the bank accounts and assets owned by the 46-year-old businesswoman and her Congolese husband Sindika Dokolo, which she described as a groundless political vendetta.

"Based on a trove of more than 715,000 files, our investigation highlights a broken international regulatory system that allows professional services firms to serve the powerful with almost no questions asked," the ICIJ wrote.

The group said its team of 120 reporters in 20 countries was able to trace "how an army of Western financial firms, lawyers, accountants, government officials and management companies helped (dos Santos and Dokolo) hide assets from tax authorities".

Dos Santos took to Twitter to refute the claims, launching a salvo of around 30 tweets in Portuguese and English, and accusing journalists involved in the investigation of telling "lies".

"My fortune is built on my character, my intelligence, education, capacity for work, perseverance," she wrote.

She also blasted "the racism and prejudice" of SIC-Expresso, a Portuguese TV station and newspaper, and member of the ICIJ, "that recall the colonial era when an African could never be considered equal to a European".

Dos Santos's lawyer dismissed the ICIJ findings as a "highly coordinated attack" orchestrated by Angola's current rulers, in a statement quoted by The Guardian newspaper.

Dos Santos herself told BBC Africa the file dump was part of a "witch hunt" meant to discredit her and her father.

A trove of files has revealed how Isabel dos Santos allegedly syphoned hundreds of millions of dollars of public money into offshore accounts
A trove of files has revealed how Isabel dos Santos allegedly syphoned hundreds of millions of dollars of public money into offshore accounts AFP / MIGUEL RIOPA

The former president's daughter headed Angola's national oil company Sonangol. Forbes magazine last year estimated her net worth at $2.2 billion.

Her father's successor Joao Lourenco forced her out of the oil company after becoming president in 2017.

Dos Santos said on Wednesday that she would consider running for president in the next election in 2022.

The ICIJ investigation said Western consulting firms such as PwC and Boston Consulting Group were "apparently ignoring red flags" while helping her stash away public assets.

"Regulators around the globe have virtually ignored the key role Western professionals play in maintaining an offshore industry that drives money laundering and drains trillions from public coffers," the report said.

Its document trove included redacted letters allegedly showing how consultants sought out ways to open non-transparent bank accounts.

One confidential document allegedly drafted by Boston Consulting in September 2015 outlined a complex scheme for the oil company to move its money offshore.

The investigation also published a similar 99-page presentation from KPMG.

None of the companies named issued immediate statements in response to the investigation.

Angola