SEOUL—Samsung Electronics Co. said it is seeking to stop the sale of Apple Inc.'s new iPhone 4S in Japan and Australia, further ramping up a legal clash with the U.S. company after a series of setbacks in courts around the world in recent days.

The Korean company said it filed on Monday for preliminary injunctions in the Tokyo District Court and in the New South Wales Registry, Australia, to stop the sale of iPhone 4S smartphones in both countries. Samsung also asked the Japanese court to stop the sale of Apple's iPhone 4...