Industrial production in September increased by 2.5 percent from August, the first gain in three months, according to a preliminary report released Wednesday by the Ministry of International Trade and Industry.The seasonally adjusted production index for the nation's mining and manufacturing sectors in September stood at 98.4 against a 100-point benchmark set in 1995, the report says. Due to the high-inventory sales ratio, which stands at 111.8 in terms of index, industrial production has remained stagnant and is expected to decline slightly for the next two months, it says.Meanwhile, combined sales at Japan's wholesalers and retailers in September dropped 8 percent to 59.3 trillion yen, marking the 11th consecutive month of year-on-year decline, according to a separate MITI report also released Wednesday.