An index that measures global peacefulness has dropped sharply for South and North Korea as tensions continue to mount on the Korean Peninsula.

The Sydney-based Institute for Economics and Peace unveiled its 2011 Global Peace Index report on Wednesday, which ranked South Korea in 50th place and North Korea in 149th place out of 153 countries surveyed. The index is a numerical measure of how at peace a country is with itself and other countries.

Compared to last year, South Korea saw its ranking slip seven notches and the North ten notches.

The report said North Korea’s tense relations with its neighbors became even more strained in 2010 following Pyongyang’s sinking of the “Cheonan” naval ship and its shelling of Yeonpyeong Island.

Iceland was found to be the country that is most at peace followed by New Zealand, Japan and Denmark.