Officials say the exchange took place shortly in an area of ocean that was the scene of November's lethal exchange between the two sides -- when North Korean shelling killed four people on Yeonpyeong Island. However, analysts say the new volleys are not much cause for concern.The two Koreas exchanged fire Wednesday along the tense western sea border, a face-off reportedly started when North Korean launched three artillery shells that landed near the disputed maritime line in the Yellow Sea, officials said.