Intel Corp. (INTC), the world's largest chipmaker, said Thursday that Korean trade regulators earlier this week raided its office in Seoul, as part of a previously announced ongoing investigation.

"We acknowledge that representatives from the Korean FTC did pay an unscheduled visit to our office in Seoul earlier this week during normal business hours," said Intel spokesman Chuck Mulloy.

Intel is under investigation in Europe and Korea for its business practices. Far smaller rival Advanced Micro Devices Inc. (AMD) filed suit against Intel in June, charging it with anti-competitive business practices.

"While it's not appropriate for us to discuss specifically what the Korean FTC is looking at, suffice it to say that we have been and will continue to cooperate," Mulloy said.

The European Union has been investigating Intel's business practices since 2001.

In April 2005, Intel said it would comply with an order to eliminate discounts that Japanese antitrust authorities said had illegally locked rivals out of the market.

At the same time, Intel disputed the Japan Fair Trade Commission's assertion it violated antimonopoly laws.

AMD has accused Intel of using everything from threats to kickbacks in building the world's top computer chip business.

Shares of Intel rose 48 cents, or 2.4 percent, to $21.15 in afternoon trade, and shares of AMD rose 86 cents, or 2.1 percent, to $41.72.