Vodafone K.K. said Monday it will add four markets to its international roaming service network June 28, bringing to 158 the number of countries and regions where its existing third-generation mobile phones can be used.

The new service areas are Iran, the islands of Martinique and Guadeloupe in the West Indies, and French Guiana in South America, Vodafone said.

Vodafone K.K., previously the Japanese unit of Britain's Vodafone Group PLC, is a Softbank Group company and will change its name to Softbank Mobile Corp. on Oct. 1.