The move escalates the tension between the firms as they vie for dominance of the mobile device market, after a series of legal clashes in Australia, Germany, and the Netherlands.

Samsung said the fresh suit, filed on Tuesday to a Seoul court, covers three utility patents and involves methods of displaying data, the user interface, and short text messages.

The companies have extended their fight to more than 30 cases in 10 countries since Apple fired its first salvo in April, claiming Samsung "slavishly" copied its iPhone and iPad models.

Samsung counter-sued, saying Apple infringed on its patents and failed to pay royalties.

Apple is also involved in patent battles in separate disputes with other smartphone makers using Google's free Android platform, the fastest growing mobile operating system, which is used by Samsung, Motorola Mobility Holdings and HTC Corp.

(Reporting by Miyoung Kim; Editing by Daniel Magnowski)

• A Permanent Economic Emergency