TOKYO--Toshiba Corp. (6502.TO) said Friday it had filed a lawsuit against SK Hynix Inc. (000660.SE) to seek damages, alleging that the South Korean chipmaker illegally obtained its NAND flash memory technology.

The Japanese tech giant said it filed the suit with the Tokyo District Court on Thursday following the arrest of a former SK Hynix employee on suspicion of illegally taking Toshiba's proprietary information and providing it to the South Korean firm in 2008.

"Moving forward, Toshiba will construct a more robust system for protecting its intellectual property and preventing its loss," Toshiba said in a statement.

SanDisk Corp. also said Thursday it had filed a civil lawsuit in California against SK Hynix and its U.S. unit, accusing the South Korean firm of misappropriation of trade secrets related to NAND flash memory. SanDisk said the employee worked at its joint venture with Toshiba in Japan and left SanDisk in 2008 to work for SK Hynix, but didn't identify the engineer.

An SK Hynix spokesman said the company has not received any formal notification or letter from either Toshiba or SanDisk over the issue.

"We're internally checking if this is true," he added.

-In-Soo Nam contributed to this article.

Write to Kana Inagaki at kana.inagaki@wsj.com

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