Austria widened an asset freeze list on Friday to include a top official at the Libyan Investment Authority (LIA) because of possible links to Muammar Gaddafi's inner circle.
The move against LIA deputy chief Mustafa Zarti, who has an Austrian passport, follows international sanctions on Gaddafi's family and associates.
Libya's main sovereign wealth fund, the LIA controls about US$65 billion. It worked to enhance Libya's credibility on the international stage by acquiring stakes in European blue-chip firms including Italian bank UniCredit and British publisher Pearson, owner of the Financial Times.
A central bank decree published in the official gazette described Zarti as a "close confidant of the regime in Libya".
It said Zarti was also a top executive of Libya's National Oil Corp, head of the Tamoil oil and petrol station group, and deputy chairman of First Energy Bank in Bahrain.
Zarti, 40, was called in for questioning by Viennese authorities on Thursday and later released, broadcaster ORF had reported, citing Interior Minister Maria Fekter.
A ministry spokesman said he did not know of Zarti's whereabouts: "We have no instructions to detain him or to take any surveillance measures."
Austria had already frozen assets linked to the Libyan leadership but Zarti was not on the original Austrian National Bank list published following sanctions adopted this week by the European Union.
Austrian media have said Vienna was pushing the European Union to add Zarti's name to its list.
The central bank chief said this week Libyan clients had about 1.2bn euros ($1.67bn) in Austrian banks and that authorities were trying to find out how much of this might be connected to people under sanctions.
Two of Austria's biggest commercial banks -- Erste Group Bank and Raiffeisen Bank International said on Thursday they had checked their records and found no money linked to people on the black list.
Bank Austria, a unit of UniCredit, said it was complying with the directive and would freeze any money it found but could not comment further because of bank secrecy rules.
Zarti, an Austrian citizen since 2006, was close to Gaddafi's son Saif al-Islam, who studied in the capital, also home to OPEC's headquarters.
Saif, a friend of the late far-right politician Joerg Haider, lived in a luxury villa on the edge of Vienna while in the country and kept his two pet white tigers in the city's zoo.