|Ties between the two Koreas plummeted following the 2010 shelling of South Korea's Yeonpyeong Island [EPA]
South Korea has conducted live-fire military drills near the disputed Yellow Sea border with North Korea, despite Pyongyang's threat to attack.
The South Korean defence ministry said the Marine Corps, which guards "frontline" islands near the flashpoint border - began the exercise at about 10am local time [0100 GMT].
About 1,400 civilians living on the islands were evacuated to bomb shelters during Monday's drill, a local official said.
South Korean military officials said they were ready to repel any attack, but there was no immediate military response from the North to what Seoul terms a "routine" drill, which ended after about two hours.
South Korean troops on the five islands fired artillery into waters southward, away from nearby North Korea, a defence ministry official said.
The North, which was notified of the scheduled exercise on Sunday, had called the drills a "premeditated military provocation'' and warned it would retaliate for an attack on its territory.
"We are monitoring every movement by the South Korean warmongers. If they provoke us, there will be only merciless retaliatory strikes,'' officer Sin Chol Ung from the North's Korean People's Security Forces told The Associated Press news agency on Sunday.
Early on Monday, Pyongyang repeated threats of retaliation. North Korea is fully prepared for a "total war",' and the drills will lead to a "complete collapse" of ties between the Koreas, the North's Committee for the Peaceful Reunification of Korea said in a statement carried by the official Korean Central News Agency.
Seoul's unification ministry, which handles cross-border ties, said the regular exercise was held to safeguard national security and was not related to inter-Korean relations.
Deadly naval clashes
Three deadly naval clashes since 1999 have claimed a few dozen lives in the waters contested by the two Koreas.
Ties between the Koreas plummeted following the 2010 shelling of front-line Yeonpyeong Island and a deadly warship sinking blamed on Pyongyang. North Korea has flatly denied its involvement in the sinking, which killed 46 South Korean sailors.
The maritime line separating the countries was drawn by the US-led UN Command without Pyongyang's consent at the close of the 1950-53 Korean War, which ended with a truce, not a peace treaty, leaving the peninsula in a state of war.
North Korea routinely argues that the line should run farther south.
The US and South Korean navies are scheduled to stage a separate joint anti-submarine drill further to the south in the Yellow Sea from Monday to Friday.
And a major annual US-South Korean drill known as Key Resolve will start on February 27 and continue until March 9. North Korea denounces such joint drills as a rehearsal for invasion.