SEOUL (Reuters) - Five years after North Korea fired shells on to a South Korean island, Pyongyang vowed on Sunday to retaliate mercilessly should Seoul hold fire drills near the border on the anniversary. 

North Korea fired scores of artillery shells at South Korea's Yeonpyeong island on Nov. 23, 2010, killing four people including two civilians in one of the heaviest attacks on its neighbour since the Korean War ended in 1953.

North Korea said it was provoked into the attack by South Korean live-fire drills in the area that dropped shells in its territorial waters.

The threat came after the two Koreas agreed on Friday to hold talks later this month, setting the stage for the first government-level meeting focused on easing tension since the two pledged to improve ties following an armed standoff in August. 

"If the South Korean military fires at the waters of the DPRK in the hotspot area of the West Sea of Korea on Monday, they will experience merciless retaliation of the Southwestern Front units of the DPRK on the five islands," the North's official KCNA news agency quoted spokesman for the southwestern front command of the Korean People's Army as saying.

DPRK is an acronym for the North's official name, the Democratic People's Republic of Korea. 

"They should not dig their own graves with war drumbeats for the preemptive strike against the DPRK but draw a lesson from the bitter defeat they suffered five years ago," the military command spokesman said.

An official at South's Joint Chiefs of Staff said they were monitoring the situation but he declined to give further comment. 

Impoverished North Korea and rich, democratic South Korea remain technically at war after their 1950-53 conflict ended in a truce, not a treaty. 

The North, slapped with U.N. and U.S. sanctions for its nuclear weapons and rocket programmes, often threatens to destroy the South, and its major ally, the United States, in a sea of flames.