North Korean patrol boat enters South Korean waters

South Korean military officials stated that a North Korean patrol boat entered South Korean waters in the West Sea on 4 June 2009. The vessel retreated within an hour, after numerous warnings were issued from a South Korean naval vessel. Unconfirmed reports indicate that the North Korean ship was chasing Chinese boats that were operating illegally in North Korean territorial waters; however, other reports have stated that the naval vessel's intrusion was a calculated plan to increase tensions between the two countries. South Korean officials confirmed that this is the third such incident involving a North Korean vessel this year. The Northern Limit Line that serves as a border between the two countries' territorial waters has been a topic of dispute since the end of the Korean War.