The North Korean military conducted two anti-ship missile tests in the West Sea in October and this month.

“The North Korean military test fired air-to-ship missiles twice, in October and earlier this month, using an IL-28 bomber jet over the West Sea,” an unnamed government official was quoted as saying by a local news agency.

The official also said that the South Korean military has been strengthening its anti-air defenses from both ships and ground positions in response to the North’s apparent move to improve its air-to-ship attack capabilities.

The tested missiles are reported to have been produced by modifying the Styx missiles first developed by the Soviet Union.

Officials at the Ministry of National Defense, however, said that they were unable to verify the news reports.

South’s anti-air weaponry includes the Cheonma ground-to-air missiles that were deployed on Baengnyeong and Yeonpyeong islands in the West Sea after the North’s attack on the latter on Nov. 23 last year.

In addition to the two missile tests, unusual developments on the northern side of the Northern Limit Line or NLL have been detected since early last month, prompting the South to increase vigilance.

In October, North Korea was reported to have moved fighter jets to bases near the NLL and relocated anti-air missiles closer to the Baengnyeong Island, while the North Korean unit responsible for the attack on Yeonpyeong Island moved artillery further down south.

With the South increasing vigilance, the number of incursions south of the NLL by North Korean military and fishing vessels has dropped dramatically from last year.

According to the data the office of Joint of Chiefs of Staff submitted to Rep. Song Young-sun, North Korean ships cross the NLL 16 times so far this year. In comparison, North Korean vessels crossed the NLL on 95 occasions last year.

By Choi He-suk  (cheesuk@heraldcorp.com)