SEOUL - The Republic of Korea (ROK) conducted one-day live-fire drills on Monday, undeterred by the Democratic People's Republic of Korea (DPRK)'s threat of retaliation.

The two-hour drills were held in waters off ROK's western border islands of Yeonpyeong and Baengnyeong, located near a tense Yellow Sea border the DPRK refuses to acknowledge.

The routine drills, which mobilized self-propelled howitzers and combat helicopters, were completed without provoking a retaliatory attack from the north of the border, military officials said.

On Sunday, the DPRK's military threatened "merciless retaliatory strikes" against what it said was a "premeditated military provocation" by ROK.

In November 2010, the DPRK shelled Yeonpyeong Island in what it said was self-defense measures against the joint military exercise by ROK and the United States near the sea border.

ROK has since fortified Yeonpyeong and four other front- line islands near the border to deter further DPRK provocation.

The volatile maritime border, called the Northern Limit Line, was drawn by the US-led United Nations Command at the end of the 1950-53 Korean War that ended with a truce.