The government was taken aback by the strong reaction from South Korea to its decision to tighten export controls on some chemicals to the country, a senior Japanese foreign ministry official said, calling it "quite surprising" while also accusing Seoul of unfairly trying to make the issue about free trade.

"These kinds of changes in export controls happen often," the official, who spoke on the condition of anonymity due to the sensitive diplomatic nature of the situation, said Tuesday. "The change is not something entirely new. ... This is not even an embargo, like the one South Korea has imposed on seafood from Fukushima."

The official's remarks epitomize the deep divide that remains between the two neighbors, with South Korea arguing the beefed up screening of three chemicals used in the production of smartphones, television screens and semiconductors will deal a blow to its economy.