The Securities and Exchange Surveillance Commission filed a complaint with prosecutors Tuesday against an investor in Kushiro, Hokkaido, alleging he manipulated the stock prices of three companies through false bids, one made over the Internet.

This is believed to be the first time the securities industry watchdog has taken action on an Internet-based stock transaction, investigative sources said.

The commission alleges that office worker Hirokatsu Furukawa, 43, bid numerous times last year for shares in a construction company listed on the Tokyo Stock Exchange's first section and two other firms in which he had stakes.

It says that although he had no intention of buying the shares he bid for in the transactions on July 29, Aug. 7 and Aug. 8, the orders gave other investors the false impression that interest was growing in the stocks, which helped lift their prices.

After the prices rose, Furukawa dumped his holdings for a profit of around 3 million yen, the sources said.

Furukawa has basically owned up to the commission's allegations, they said.

According to the sources, Furukawa allegedly placed several buy orders ranging from 1.91 million to 4.55 million shares through several unnamed brokers, then sold 140,000 to 200,000 shares of each company. It was not clear whether Furukawa actually had the funds to purchase such a large amount of shares.

The complaint was filed with the Kushiro District Prosecutor's Office.