BERN, Switzerland (AP) _ Swiss authorities said Tuesday they temporarily have frozen five bank accounts that U.S. investigators believe are tied to allegedly illegal stock dealings in the United States.

The accounts were frozen for 30 days last Friday after the U.S. government informed Switzerland it planned to ask for judicial help in an insider trading case involving Nahum Vaskevitch, a former official at Merrill Lynch & Co. Inc.'s London office, and Israeli businessman David Sofer, said Joerg Kistler, a Justice Ministry spokesman.

Securities and Exchange Commission investigators in Washington believe the two made some $4 million in illegal profits on U.S. stock market transactions by using confidential information.

The frozen accounts at the Zurich branch of Credit Suisse bank are in the names of individuals as well as companies, Kistler said, but did not elaborate.

U.S. authorities plan to cite charges of improper use of company secrets in a formal judicial assistance request, he said.

Such acts are also criminal offenses in Switzerland, a prerequisite for granting judicial assistance, extending the freeze and any lifting of Swiss bank secrecy.

The United States cited similar charges in successfully obtaining waivers of Swiss bank secrecy in other insider probes in recent years.