A Swiss national detained over allegations of attempted extortion involving a Saudi Arabia-based oil and gas company has admitted to committing blackmail, Thai police said on Thursday.

Xavier Justo, a former executive of PetroSaudi International Ltd, was arrested on a Thai resort island last month following allegations by the company that he had demanded a payment in exchange for not disclosing confidential information.

“From our investigation, Xavier Justo admitted that he attempted blackmail,” Thai national police spokesman Prawut Thavornsiri told a news conference.

Justo has not been formally charged.

Police officials did not provide any details on the documents and information in the alleged blackmail attempt, and whether they were linked to Malaysia's troubled state investment fund 1MDB, which is being investigated for misappropriation and graft after several leaked documents were released in the media.

Some of the leaked documents were related to a deal between 1MDB and PetroSaudi several years ago.

The Malaysian state fund said after Justo's arrest last month that it would fully cooperate with the Thai investigations.

PetroSaudi said after Justo's arrest that it had been a victim of "a regrettable crime that has unfortunately been politicised in Malaysia".

Justo is being held in a Bangkok jail, and the investigation continues. - Reuters