Isabel dos Santos, the daughter of former Angolan president Jose Eduardo dos Santos, has denounced a court order to seize an estimated $1 billion worth of her assets, terming it "politically motivated".

46-year-old Isabel is often described as Africa's richest woman, with a fortune estimated at $2.2 billion by Forbes magazine.

An Angolan court on 23 December ordered her bank accounts to be frozen and her shares in local companies seized, according to Angola's state news agency.

The move is seen as part of President Joao Lourenco's anti-corruption drive.

"At a time when it is vital for the Angolan economy to attract foreign investment, this politically motivated confiscation order is a bad signal to the private sector." Isabel wrote on Twitter.

She vowed to "use all the instruments of Angolan and international law at my disposal to fight this order and ensure the truth comes out."

Towards the end of his tenure, former president Jose Eduardo dos Santos appointed his daughter Isabel as the head of Angola's state-owned oil firm, Sonangol. Months after Lourenco took power however, he sacked Isabel from the position.

Other than Isabel, another of dos Santos's children is also in court for graft.

Jose Filomeno dos Santos is currently being tried in Angola for allegedly helping to smuggle $500 million out of the country when he was head of Angola's Sovereign Wealth Fund. He denies the charges.