South Korea's antitrust watchdog plans to fine six steelmakers over 100 billion won for colluding to fix prices of steel reinforcement products.

The Fair Trade Commission (FTC) said Sunday that Hyundai Steel and five other steelmakers will be fined a combined 119 billion won for rigging prices between May 2015 and December 2016.

Of the six firms, the FTC also plans to lodge a complaint with the prosecution against five steelmakers, including Hyundai Steel and Dongkuk Steel.

The six companies, whose combined share in the local steel reinforcement market tops over 80 percent, are accused of rigging prices of the products to prevent the prices from falling under a certain level amid a rise in imports from China.