SEOUL—Samsung Electronics Co. escalated its fight with Apple Inc. over the appearance of smartphones, filing a new lawsuit in the U.S. Thursday, and introducing its second-generation Galaxy S phone in its home country of South Korea with few apparent changes in appearance from the model Apple alleges copies aspects of its iPhone.

The new phone retains some of the icons that Apple alleges Samsung copied from it, such as a phone receiver against a green background that launches telephone functions and a gear wheel to reach settings. But a photo-app icon now resembles a camera rather than flower petals; Apple's icon is a sunflower.

Samsung representatives in Seoul didn't respond Thursday to requests for comment on the appearance changes. Later Thursday, Samsung filed a lawsuit in federal district court in San Jose, Calif., accusing Apple of violating 10 patents on cellphone technology and design. The suit was announced by Samsung in Seoul on Friday Asia time.

In response, an Apple spokeswoman repeated the statement the company made when it filed suit against Samsung, saying that Apple needed to protect itself "when companies steal our ideas."

After Apple initially filed suit against Samsung, Samsung filed three patent lawsuits against Apple in South Korea, Japan and Germany.