A South Korean diplomat to the United Nations says that North Korea’s artillery attack on Yeonpyeong Island violated the Korean War Armistice and the U.N. Charter.

Deputy Representative to the U.N. Office at Geneva Im Han-taek made the remark during the Convention on Certain Conventional Weapons that was held in Geneva on Thursday, local time.

He said the North’s attack was a violation of the spirit of the Korean War Armistice.

Im added that the North, by launching the attack, had engaged in a prearranged, illegal provocation that goes against inter-Korean agreements and the U.N. Charter.

He stressed the need for a stern response, noting that the shelling marked the first time since the Korean War for the North to destroy private houses in the South.

A total of 112 countries are taking part in the Convention on Certain Conventional Weapons. The U.N. Office at Geneva defines the convention as body that aims to “ban or restrict the use of specific types of weapons that are considered to cause unnecessary or unjustifiable suffering to combatants or to affect civilians indiscriminately.”