LISBON (REUTERS) - Angola could issue an international arrest warrant for billionaire Isabel dos Santos if she fails to cooperate with a fraud investigation in which she has been named as a suspect, its chief prosecutor was quoted as saying.

Angola has named Ms dos Santos, the daughter of former president Jose Eduardo dos Santos and reputedly Africa's richest woman, as a suspect over alleged mismanagement and misappropriation of funds while she was chairman of state oil firm Sonangol in 2016-2017. She denies wrongdoing.

"At this moment, the concern is to notify (the suspects) and assure that they voluntarily come to face justice," Mr Helder Pitta Gros said in Luanda late on Wednesday (Jan 22) before travelling to Lisbon on Thursday, according to Portugal's Lusa news agency.

Failing that, his office would resort to legal instruments at its disposal, one being an international warrant.

Portuguese newspaper Expresso said several people linked to Ms dos Santos were also named as formal suspects, including Mr Nuno Ribeiro da Cunha, director of private banking at small Portuguese lender Eurobic and manager of Angola's oil firm Sonangol's account at the bank.

Police said on Thursday (Jan 23) Mr Ribeiro da Cunha was found dead at the garage of his house in Lisbon on Wednesday night.

He had apparently committed suicide by hanging. He had tried to commit suicide earlier this month, police said.

No one at Eurobic was immediately available for comment.

Eurobic, in which Ms dos Santos has owned a large stake, said on Thursday she had decided to sell the stake.

Meanwhile, Mr Mario Leite da Silva, who resigned as chairman of Banco de Fomento Angola (BFA) on Monday, was also named a formal suspect by Angola's public prosecutors.

In his resignation letter, which was seen by Reuters, Mr Silva made no reference to recent events linked to Ms dos Santos, citing instead a December decision by BFA's controlling shareholder Unitel not to name him among board members for the next three years.

Telecoms firm Unitel is part-owned by Ms dos Santos.

Portuguese Banco BPI, a unit of Spain's Caixabank, is another major shareholder in BFA.

Separately, auditors PwC said the firm had "taken action to terminate any ongoing work for entities controlled by members of the dos Santos family" following what it said were "very serious and concerning allegations", and had begun an inquiry.

Ms Isabel dos Santos, who amassed her fortune during her father's decades-long presidency, has said allegations against her are politically motivated. She could not immediately be reached for further comment on Thursday.