South Korea's imports of bituminous coal in September rose 4.6 percent from a year earlier due to lower imports of alternative energy resources including natural gas, industry data showed on Thursday.

South Korea, the second-largest importer of Australian coal, a benchmark for Asia, bought 6.85 million tonnes of coal in September, up from 6.55 million tonnes a year ago, the International Trade Association (KITA) said.

South Korea paid an average of $139 per tonne in September, nearly double the $71 per tonne last year, but the price was sharply lower than the record of around $200 a tonne in early July.

Coal prices have fallen to around $103 per tonne.

Coal, mostly used for heating by utilities, accounts for about 40 percent of South Korea's power generation, the second largest after nuclear power generation.

Imports from Australia were at 2.56 million tonnes, the largest, with Indonesia following with 1.8 million tonnes.