Isabel dos Santos denies the charges against her, saying they are 'politically motivated'.

Angola has frozen the assets of Isabel dos Santos, the billionaire daughter of former Angolan President Jose Eduardo dos Santos in a sign that President Joao Lourenco is taking a tougher line against the former first family.

Isabel dos Santos - nicknamed the Princess - denied allegations of financial irregularities on Tuesday, calling the claims "politically motivated".

She is under investigation for alleged irregularities involving state companies including the OPEC nation's giant state oil company Sonangol.

The allegations are riddled with "obvious lies, errors and omissions", she said.

"This court decision, which is the outcome of an injunction that was not communicated to the parties, is clearly arbitrary and politically motivated."

Isabel later told Reuters news agency that she had never been summoned or questioned by an Angolan court or prosecutors.