The Securities and Exchange Surveillance Commission is examining 25 Japanese-language Web sites for fraudulent activity related to securities transactions, commission officials said Tuesday.

The suspect Internet sites were discovered during an international sweep of thousands of Web sites on March 28, "International Internet Surf Day." The operation was conducted by 21 regulatory authorities from 18 countries who searched and identified suspicious sites.

Of the 25 sites, 12, including nine involving cross-border activity, offer high-yield or principal-guaranteed investment products. One advertises a fund with an annual return of up to 2.5 times the principal investment, they said.

Other sites solicit business by promising that the price of a specific stock issue will rise, or by spreading rumors about specific issues, the securities watchdog said.

The SESC has not yet identified the operators of the sites, officials said.

Surf Day, a first-time effort begun by the International Organization of Securities Commissions, is aimed at increasing international coordination to crack down on Internet-based fraud.

Each regulator used search engines on the Net to look for fraudulent sites.

Worldwide, more than 1,000 sites were identified for followup reviews, including over 250 involved in cross-border activity, the IOSCO Technical Committee said in a statement released the same day.

The review is now under way and could result in legal action by regulators in each country and international cooperation when appropriate, IOSCO said.