Softbank Corp. announced Wednesday that it returned to profitability during the April-September period, helped by its acquisition of Vodafone Group PLC's Japanese mobile-phone unit and a turnaround in its broadband Internet and fixed-line telecom business.

The Tokyo-based Internet and telecommunications conglomerate posted a group net profit of 14.4 billion yen during the first half, compared with a 4.18 billion yen loss the previous year. Group operating profit climbed to a record 112.6 billion yen, compared with 4.4 billion yen the prior year.

The group's overall sales increased by 114 percent to 1.12 trillion yen. Its mobile phone business accounted for 52 percent of those sales.

The company, which recently entered the highly competitive mobile phone market, said its operating profit in its mobile business reached 56.6 billion yen. Softbank acquired Vodafone K.K., the Japanese unit of Britain's Vodafone Group, in April for 1.75 trillion yen.

In the broadband business, Softbank, which is the largest domestic asymmetric digital subscriber line operator, posted an operating profit of 11.67 billion yen, reversing a loss of 1.01 billion yen in the previous year.

Despite the strong half-year performance, things are still not rosy for Softbank.

Following the introduction of the mobile number portability service on Oct. 24, Softbank has had to stop processing sign-up and cancellation applications for its mobile phone service several times due to an overload of its computer system.