Vassilev was at the centre of a scandal last year when a bank he majority-owned, Corporate Commercial Bank (Corpbank) (>> Korporativna targovska banka AD Sofia), was hit by a run on deposits and shut down.

He was subsequently charged with embezzlement and has accused unnamed "political hyenas" in Bulgaria of trying to wrest control of his businesses while he awaits the outcome of extradition hearings in Serbia.

LIC33 Group, a private investment company set up for the transactions, said it had bought stakes in the Balkan country's largest telecom operator by revenue, Vivacom, and five other unlisted businesses.

It went out of its way to deny that LIC33 was a front for Vassilev. But the government said it wanted more information about the origins of LIC33's funds to ensure they were lawful.

LIC33 is owned by its chairman, Pierre Louvrier, a Belgian investor formerly involved in operations in Russia as head of private investment firm CFG Capital. He quit CFG in November, according to his LinkedIn profile, though he remains a non-executive director of Rusgrain Holding (>> RusGrain Holding OAO).

Vassilev has made no mention of the deals, although he regularly publishes statements on his website.

A spokeswoman for Vivacom said it had not been informed of any shareholder changes. Russia's VTB Bank (>> Bank VTB OAO), which owns a third of the telecoms company, has declined to comment.

FUNDING

"We are here to stay, we are here long-term. Once again we are awaiting regulatory approvals, but the former shareholder is not coming back," Louvrier said at a news conference in Sofia.

LIC33 said it would conduct due diligence on the companies it is buying into and hold talks with international banks to pay out and refinance existing debt, much of it owed to Corpbank.

LIC33 also said it wanted to buy the stakes held by Vivacom's other shareholders by the end of 2015.

"Our key task before we have a position towards the announced investors, is to explore the origin of the funds," the government said in a statement.

"It is important so that we can guarantee that investments in a member state of the EU are carried out only with funds from legal economic activity."

LIC33 was confident it could reassure the government.

"As Mr Louvrier said, the funds are coming from him and from international banks. There will be no secrets," a spokesman told Reuters.

(Editing by Matthias Williams and Mark Potter)

By Tsvetelia Tsolova