SEOUL -- South Korea's foreign exchange authorities on Monday issued a verbal intervention over excessive volatility in the foreign exchange market.

The Ministry of Economy and Finance and the Bank of Korea (BOK) said in a joint statement that the FX authorities are closely monitoring the possibility of herd behavior, with caution, in the process of the local currency's expanded volatility, caused by internal and external factors.

It marked the first verbal intervention by the authorities in one and a half years since April last year when the won versus US dollar exchange rate came closer to 1,400 won per dollar amid geopolitical tensions in the Middle East.

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The won versus dollar exchange rate started at 1,430.0 won, up 9.0 won compared to the previous trading day.

The rate soared to 1,434.0 won during market hours, recording the highest in five months since early May.