South Korea's producer prices dropped slightly from a year earlier in September on a large cut in prices of coal and petroleum products, central bank data showed Wednesday.

The producer price index for September came to 99.24, down 1.1 percent from the same month last year, according to preliminary data from the Bank of Korea.

Producer prices serve as an indicator of future consumer inflation.

The September index marked a slight increase from a revised 99.00 in the previous month.

Prices of manufactured goods remained unchanged in September from a month earlier, while prices of agricultural and fisheries goods gained 5.4 percent on-month in September.

Utility prices, including electricity and water, lost 0.1 percent from the previous month, according to the BOK. (Yonhap)