Customs authorities will crack down on illegal trade and foreign exchange dealings by the country's exporters in the wake of the high currency rate.

According to the Korea Customs Service's inspection plan announced on Tuesday, authorities will look into one-thousand-138 companies that had large discrepancies between the reported export and import data and trade payments processed through banks.

The customs agency will focus on firms that deliberately fail to report payments in a bid to exploit fluctuations in the foreign exchange market.

It will also inspect for irregular payments with misuse of crypto currencies and flight of assets overseas.

The crackdown comes after the gap between trade payments received or paid through banks and the reported trade volumes reached 290 billion U.S. dollars last year, the largest amount in five years.

The agency plans to form a task force to continue the inspections until the exchange rate stabilizes.