South Korea¡¯s top currency official has fired a warning at Japan: his nation has stepped up scrutiny of the yen¡¯s tumble against the won after damage to exporter earnings.

¡°Korean companies face bigger difficulties this year than last,¡± said Song In-chang, the South Korean Finance Ministry¡¯s director general in charge of foreign exchange market policies. ¡°What¡¯s different is that we have been paying attention to the won-yen rate since last year, whereas the won-dollar was our main focus before that.¡±

The currency¡¯s gains against the euro have also caught Song¡¯s attention, he said during an interview in Sejong, south of Seoul, last Thursday.

The won is at its strongest level against the yen and the euro since at least 2008, putting pressure on exports that have fallen for four straight months this year, the longest streak since 2009.

Companies from Hyundai Motor Co. to LG Electronics Co. and Samsung Electronics Co. reported earnings last month that declined from a year ago and all three said the currency¡¯s strength contributed to the results.

Song said that while the government doesn¡¯t target any specific level for the won, it could ¡°fine-tune¡± movements to ease any ¡°herd behavior¡± in the currency.

The won has gained about 40 percent against the yen since Prime Minister Shinzo Abe took office in late 2012. It¡¯s up about 17 percent versus the euro and little changed against the dollar over the same period, according to data compiled by Bloomberg.

¡°Last year, the won¡¯s declines against the dollar offset the impact from the gains against the yen, but this is no longer the case,¡± said Song, 53.

Still, South Korea has no intention of intervening in the currency market for the sake of exporting companies, Song said.

Hyundai Motor cited weakening of the euro and other emerging-market currencies for profit declines in the first quarter. LG Electronics last week said its first quarter sales growth was marginal due to negative currency impact.

That¡¯s a notable contrast to Toyota Motor Corp., Japan¡¯s biggest company, which is forecasting a second-straight record annual profit as it benefits from a weaker yen.

South Korea¡¯s trade ministry said on Friday that the weakening of the yen and the euro had hurt exporters from automakers to machinery manufacturers. Shipments to Japan fell 12.6 percent in April from a year earlier while exports to Europe dropped 11.9 percent.

Separately, Song said the government may sell yuan-denominated bonds for the first time.

¡°We may issue if we need to set benchmark costs for local companies,¡± Song said, without giving further details.