TOKYO (AFP) -- In under a decade flamboyant, Ferrari-driving tycoon Takafumi Horie built one of Japan's top Internet empires with an aggressive expansion drive that made him few friends in the establishment.

But now the 33-year-old's brash style is under a new microscope with public prosecutors overnight raiding the offices of his company, Livedoor, for suspected illegal securities trading.

The scandal around the pudgy, spiky-haired entrepreneur -- who was courted by the premier to run for parliament next year -- caused concern among the government and sent Japanese share prices spiraling downward Tuesday.

If the Livedoor group misled investors, "it would be a matter of concern as it hurts market confidence," said Kaoru Yosano, the economy minister who is also in charge of financial services.

Horie, who has famously declared "All the evils come from aged business managers" and "I will kill newspapers and television", insisted it was business as usual.

"I will strive to expand business as I did in the past," he told a news conference, apologizing to investors for any worries they may have.

Horie, nicknamed Horie-mon after a Japanese cartoon character, ruled out immediate resignation as Livedoor president but said the group was conducting its own in-house investigation into the allegations.

"It would be rather irresponsible to speak about whether I will step down or stay when we are yet to get hold of the current situation," he said.

According to news reports, Livedoor Marketing, an affiliate of Livedoor, allegedly submitted false documents on its purchase of a publishing firm in October 2004.

Investigators waited until nightfall before marching into Livedoor's headquarters on the top floor of Roppongi Hills, one of Tokyo's premier business addresses home to some of Japan's leading IT entrepreneurs.

Under the glare of the television cameras and about 100 reporters who were tipped off in advance, they then marched to continue the search at Horie's home in the office, shopping and residential complex.

The university drop-out, who eschews a suit and tie in favour of T-shirts, has been criticised for following a ruthless, Wall Street-style of capitalism.

He angered many in Japan's corporate old guard when he launched an unsuccessful takeover battle for the nation's most widely watched television network, Fuji Television -- a bid that saw him labelled by critics as a corporate raider. That followed a failed attempt to buy a professional baseball team.

Horie has regularly appeared on television game shows, has written several books on how to be a successful entrepreneur and his picture often appears in the newspapers accompanied by his friend.