Angola has frozen the assets of Isabel dos Santos, the billionaire daughter of the country’s previous leader, in a sign that the country’s current president is taking a tougher line against the former first family.

President João Lourenço ended former-President José Eduardo dos Santos’ nearly 40-year grip on power in 2017 and has been trying since then to erase the influence of his predecessor and reform Angola, sub-Saharan Africa’s third-largest economy. But Mr. Lourenço is under pressure as the country continues to contract under his watch.

Ms. dos Santos said the asset freeze ordered by a court was “politically motivated” and that the case against her had been held in total secrecy.

“The judgment contains statements which are completely untrue,” she said in a statement. “It would have been easy to dismantle them in an open court.”