Angolan billionaire Isabel dos Santos on Monday lost an appeal to overturn an order freezing up to £580-million of her assets as part a lawsuit at London's High Court.

Dos Santos – Africa's first female billionaire, whose father Jose Eduardo dos Santos ruled Angola for 38 years until 2017 – is being sued by Angolan telecoms operator Unitel.

Unitel was granted a worldwide freezing order over dos Santos' assets in December and the Court of Appeal on Monday rejected her appeal against that decision.

Dos Santos has faced corruption accusations in Angola for years. She denies the allegations and says she is the target of a long-running political vendetta.

She is being sued by Unitel over loans it made to separate Dutch company Unitel International Holdings (UIH) in 2012 and 2013, when she was a Unitel director, to fund UIH's acquisition of shares in telecoms companies.

Dos Santos owns and controls UIH, the Court of Appeal said in its ruling.

Unitel and UIH are not related despite bearing the same name, and dos Santos resigned as a director of Unitel in 2020.

The loans were not repaid and around £300-million is outstanding, Unitel's lawyers argued at the High Court.

But dos Santos – who claims to be the victim of a "campaign of oppression" by Angola – says Unitel is itself responsible for UIH's inability to repay the loans because of its alleged role in Angola's unlawful seizure of UIH assets.