PARIS, JAN. 18 -- Italian financier Carlo De Benedetti today announced two startling investment moves designed to "lay the foundations" for creating the first pan-European holding company.

The moves by De Benedetti, chairman of the Italian communications giant Olivetti Corp. and a leading international takeover artist, are aimed at giving him control over Societe Generale de Belgique S.A., Belgium's largest holding company with assets of about $2.8 billion.

Observers were surprised that De Benedetti would try to gain control of a Belgian company that is viewed as the economic, industrial and financial backbone of the nation. The financier's strategy -- trying to get at Societe Generale through French companies -- is also considered radical.

De Benedetti said his French holding company Cerus S.A. was boosting its stake in Dumenil-Leble S.A., a French investment company, to 25 percent from the current 4.99 percent.

De Benedetti also disclosed that Cerus now controls 7.8 percent of Societe Generale, and that Dumenil-Leble had gained control of 10.8 percent of the Belgian company's shares.

The financier said that in addition to those two stakes in Societe Generale -- which together total 18.6 percent -- his Cerus group had notified Belgian authorities of plans for a public share sale aimed at "significantly boosting" its stake in the Belgian giant.

The announcement was not more specific. But in Brussels, Belgium, Societe Generale announced that Cerus had indicated it wanted to buy an additional 15 percent of the Belgian company's shares, or 4.2 million of its 28.2 million outstanding shares.

The chairman of Societe Generale, Rene Lamy, said that in an attempt to block Cerus' action, Societe Generale would issue 16 million new shares of stock, representing a 60 percent increase in its capitalization.

It was unclear, however, whether Societe Generale would be allowed to proceed with the issuance of new shares, since Belgian securities law prohibits such actions when taken in response to a takeover offer.

At about the same time as Lamy's announcement, the Brussels Stock Exchange indefinitely suspended trading in shares of Societe Generale, whose holdings include Belgium's largest bank.

The suspension was imposed shortly after the Belgian Finance Ministry, citing "irregular transactions," recommended that trading in Societe Generale be halted for at least 48 hours.

The Finance Ministry later disclosed that De Benedetti planned to arrive in Brussels Tuesday for talks with Finance Minister Mark Eyskens and Philippe Maystadt, the economics minister and vice premier. No details were announced.

De Benedetti's moves reflect expectations that the European Community will succeed in its effort to remove all remaining barriers to the free movement of goods and capital across borders of member countries by 1992.

Societe Generale has stakes in more than 1,200 companies spread across virtually every industrial and financial activity in Belgium. It was founded in 1822 by Dutch King William to industrialize what was then the Netherlands' southern flank.