South Korea, the world's second-largest LNG buyer after Japan, imported 3.67 million tonnes of LNG last month, compared with 2.31 million tonnes in September 2010, Korea Customs Service data showed. The country's LNG inventory stood at over 3 million tonnes as of Tuesday, and the country plans to build nearly 3.5 million tonnes of inventory by mid-November for winter demand, according to a government source on Tuesday. State-run Korea Gas Corp (KOGAS) has sold gas equivalent to 1.95 million tonnes of LNG domestically in September, up 15.8 percent from a year earlier and led by strong demand for power generation. The amount was equivalent to 86.3 billion cubic feet of natural gas. For coal, the country's September imports rose 30.3 percent to 11.45 million tonnes from 8.79 million tonnes a year earlier, data from the Korea Customs Service also showed on Saturday.