Prosecutors said Jose Filomeno dos Santos had been placed in detention due to the complexity and seriousness of the issue.

He or his legal representatives have not yet commented.

Mr dos Santos was sacked as head of oil-rich Angola's $5bn dollar sovereign wealth fund after Joao Lourenco became president last year, vowing to eradicate nepotism and corruption.

In March, Mr dos Santos was formally accused of fraud over the alleged illegal transfer of $500m from the central bank.