Softbank Mobile Corp. Chairman and CEO Masayoshi Son said the mobile phone company now has more than 30 million subscribers, or double the number it had in 2006 when Softbank Corp. bought the local phone assets of Vodafone Group PLC.

Softbank Mobile's contracts spiked after it began selling the iPhone in 2008 as the nation's sole marketer of Apple Inc.'s smartphone. That monopoly ended in November 2011, when the au mobile phone unit of KDDI Corp. started selling it.

Of Japan's three major mobile carriers, NTT DoCoMo Inc. logged 60.54 million subscribers as of July 31, followed by 35.72 million at au and 29.92 million at Softbank, according to the Telecommunications Carriers Association. Outside of the three, eAccess Ltd. said it had 4.13 million subscribers as of June 30.

Son revealed the figure in a Twitter message Sunday.