A memorial service was held on South Korea's Yeonpyeong island Friday as the country marked the second anniversary of the shelling on the island by the Democratic People's Republic of Korea (DPRK).

Public Administration and Security Minister Maeng Hyung-kyu joined mourners to pay tribute to those who were killed in the artillery bombardment two years ago.

The attack, which took lives of two South Korean marines and two civilians, was the first time civilians had been targeted since the 1950-1953 Korean War.

The DPRK said the artillery attack was an act of self-defense against a live-fire drill by the South, which, it claimed, resulted in shells falling on its side of the sea border.

The event was held despite a threat from the DPRK to repeat the artillery attack on the border island if South Korea went ahead with commemorative events marking the second anniversary of the shelling.

Minister Maeng said in his speech that concrete efforts by the international community are required to bring change to the DPRK, while denouncing the country for resulting in instability on the Korean Peninsula. "The DPRK's indiscriminate firing of shells on civilians was a crime against humanity,"Maeng said."It was a behavior that dashed cold water on desires of South Koreans and the world for peace on the Korean Peninsula."

A ceremony celebrating the completion of a national security training center on the island was also held.

The center, built as part of the efforts to turn the island into a site of security education, houses the wreckage of three houses that were damaged in the artillery bombardment.

It aims to give visitors a first-hand experience of what it was like at the time of attack and raise security awareness.