South Korea confirmed on Tuesday it had begun to impose a tariff of over 500 percent on rice imports from the start of the year, but added that five members of the World Trade Organization had raised concerns over the level.

Asia's fourth-largest economy wants to protect farmers after scrapping a cap on politically sensitive imports of the main staple in line with international trade commitments made via the WTO.

In September, it set the tax at 513 percent, saying that was the highest rate possible under parameters set by the WTO.

A joint statement by the country's finance, trade and agriculture ministries on Tuesday added that Seoul would hold bilateral talks with its main foreign rice suppliers to ease concerns over how the rate was calculated. Those countries are the United States, China, Thailand, Vietnam and Australia.

South Korea is broadly self-sufficient in the grain, but under the WTO agreement, it purchased 408,700 tonnes of foreign rice in 2014, 9 percent of its demand.

Under the new scheme, Seoul is still required to import at least 408,700 tonnes a year. The import of 408,700 tonnes attracts a tariff of 5 percent, and the 513 percent applies to shipments above that level.