The Korean won strengthened to a nine-month high against the U.S. dollar Friday, after suspected market-smoothing operations by the nation's foreign exchange authorities. The won was quoted at 1,418 won per dollar as of around 6 a.m., marking the strongest level since Oct. 20 last year. The won had advanced to as high as 1,419 won per dollar Thursday night (Seoul time) but pared gains and traded at the 1,430-won level as of 9:37 a.m. The won's appreciation was in line with a gain in the Japanese currency. At one point in New York trading, the yen rose to about 158 per dollar, hitting the strongest level in more than two years. Lee Min-hyuk, an analyst at KB Kookmin Bank, said the correlation between the won and yen raised speculation that both Korean and Japanese foreign exchange authorities might have intervened in the markets. The overnight strength of the won and the yen "could suggest the authorities in Korea and Japan may have intervened together," Lee speculated.