N Korean military helicopters deployed near maritime border

South Korean media is reporting that North Korea has deployed around 20 helicopters at two bases near South Korea's Baeknyeong Island in the West Sea since May. Baeknyeong Island is South Korea's northernmost island that lies just south of the Northern Limit Line, the (disputed) de facto maritime border with North Korea.

North Korea operates no dedicated attack helicopters, however it's Mi-2, Mi-4 and Mi-8 transport helicopters can be armed with unguided rockets, with a South Korean military source indicating that the helicopters are deployed "independently of any military exercises".

A quick glance at Google Earth would indicate the two closest North Korean airbases are Taetan and Kwail.