South Korea's producer prices rose to a four-year high in August as the cost of farm products soared due to the unprecedented heat wave.

According to data by the Bank of Korea on Friday, the producer price index, a barometer of future consumer inflation, reached 105-point-43 last month, up half of a percent from a month earlier.

The figure is the highest reading since August 2014 when it hit 105-point-57. 

Producer prices rose three percent last month from a year earlier. 

The index of agricultural products jumped 18-point-three percent on-month in August, the steepest hike since September 2010 when it rose 18-point-eight percent. 

In particular, spinach prices tripled from the previous month. 

Prices of industrial goods, petrochemicals and gas rose point-one percent on-month. Service sector prices also gained point-one percent.