South Korean stocks opened higher Monday as the upgrade of the country's rating by Moody's over the weekend boosted investor sentiment here.

The benchmark Korea Composite Stock Price Index added 4.51 points, or 0.23 percent, to 1,979.83 in the first 15 minutes of trading.

Petrochemical shares bounced back from last week's loss.

Top refiner SK Innovation rose 2.28 percent, and No. 3 S-Oil jumped 4.07 percent.

Korea Aerospace Industries sank 3.6 percent after a T-50 trainer jet crashed during an air show in Indonesia on Sunday, killing the two pilots aboard. The cause of the crash of the South Korea-made light attack fighter is not yet known.

On Saturday, Moody's Investors Service upgraded South Korea's credit rating one level to Aa3, citing the nation's resilient credit metrics and prudent fiscal stance.

The local currency was trading at 1,177.4 won against the U.S. dollar as of 9:15 a.m., up 5.6 won from Friday's close. (Yonhap)