BRUSSELS, BELGIUM -- A financial group controlled by Italian investor Carlo De Benedetti announced yesterday it had sweetened its offer to buy a major stake in Societe Generale de Belgique SA, Belgium's largest holding company.

De Benedetti already holds an 18.6 percent stake in Societe Generale through the French firm Cerus, which said yesterday it was willing to pay 4,000 francs, the equivalent of $114, per share to gain another 15 percent of the company's stock.

Cerus had said it would pay 3,400 francs per share but upped its bid following sharp fluctuations in Societe General stock last week. Societe Generale stock closed at 3,750 francs on the Brussels stock exchange Friday.

If De Benedetti is successful in acquiring the shares, he would have effective control of Societe Generale, which has a stake in one-third of Belgium's economy.

Cerus also said yesterday it would no longer abide by the rules of a regulatory banking commission, set following its Jan. 18 original offer, unless Cerus gets the go-ahead for its proposal Tuesday.

The commission asked De Benedetti to refrain from buying Societe Generale shares until a decision is reached on the validity of his offer. Failing a decision Tuesday, "we will act as we please in all freedom, on all matters," said Cerus' chief administrative officer Alain Minc.

More than 7 million of the company's 28 million shares changed hands last week.