By Sergio Goncalves and Catarina Demony
LISBON (Reuters) - Portugal's market watchdog launched inquiries into various firms where Angolan billionaire Isabel dos Santos holds stakes, it said on Thursday, after Angola's chief prosecutor said she could face an international arrest warrant if she fails to cooperate in a fraud investigation.
Angola has named 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 chairwoman of state oil firm Sonangol in 2016-2017. She denies wrongdoing.
In Portugal, Angola's former colonial power, dos Santos holds significant stakes in several important firms.
The head of the country's market regulator CMVM, Gabriela Figueiredo, said it launched inquiries earlier this week into two of those companies, oil company Galp Energia and telecoms firm NOS, as well as into unspecified auditing firms.
Galp declined to comment and a NOS spokesman said the company had no comment so far.
Angola's chief prosecutor Helder Pitta Gros was quoted by Portugal's Lusa news agency as saying late on Wednesday, before traveling to Lisbon on Thursday, that his office sought dos Santos and other suspects "to voluntarily come to face justice".
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 dos Santos were also named as formal suspects, including Nuno Ribeiro da Cunha, director of private banking at small Portuguese lender Eurobic and manager of Sonangol's account at the bank.
Police said on Thursday Ribeiro da Cunha was found dead at the garage of his house in Lisbon on Wednesday night, after apparently committing 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 dos Santos has owned a large stake, said on Wednesday she had decided to sell the stake.
'CONCERNING ALLEGATIONS'
The CMVM regulator said it wants to find out if there is any relevant information that Galp and NOS should have provided to CMVM but did not.
Figueiredo said hundreds of thousands of files about dos Santos, dubbed the "Luanda Leaks" and released on Sunday, were of "enormous importance" for the market regulator.
The documents were obtained by the International Consortium of Investigative Journalists (ICIJ) and released by several news organizations.
The media reports focused on alleged financial schemes used by dos Santos to build her business empire, including transfers between Angola and Dubai. Dos Santos, who has been living abroad, said on Sunday that allegations made against her were "completely unfounded".
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.
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.
Authorities in Angola froze dos Santos' assets there in late December.
Chief prosecutor Pitta Gros arrived in Lisbon on Thursday to meet his Portuguese counterpart Lucilia Gago. He told reporters upon arrival he would seek help from the Portuguese prosecutor's office "on many matters", but declined to specify if they would discuss the dos Santos case.