North Korea is building a facility to house rocket launching systems only 2.8 miles from South Korea's Yeonpyeong Island, reported the Korea Times on Tuesday. The North Korean facility is reportedly being built on Gal Island and could house 122-millimeter multiple launch rocket systems.

North Korea has reportedly begun to build camps on the island, and South Korea has taken notice. “We understand that the North is still constructing [the camps]," Defense Ministry spokesman Kim Min-seok said at press briefing Tuesday, according to the Korea Times. "The ministry is paying keen attention to Pyongyang's actions there, including the deployment of weapons. This is because such a base will pose a severe threat to defense operations of the South Korean military, considering the location of Gal Island and the distance between Yeonpyeong Island and the Northern Limit Line." 

The Northern Limit Line is the disputed maritime border in the Yellow Sea between the Koreas. The South Koreans believe Gal Island will be used to house the rocket systems or a post to watch South Korean warships, the Korea Times reported. North Korea used the multiple rocket systems in a 2010 attack that killed two marines and two civilians on Yeonpyeong Island.

Rocket launching systems built so close to the border would raise tensions in the area, with the facility posing a serious threat to Yeonpyeong and South Korean patrol boats near the Northern Limit Line. North Korea does not recognize the NLL and wants the frontier drawn farther south. North Korea also warned in early May that it would fire on patrol boats that violated the Yellow Sea border it claims.

Further raising tensions, North Korean leader Kim Jong Un praised on Tuesday his military's test of a submarine-launched ballistic missile, despite international concerns about the region's security. South Korea said on Monday that it would retaliate after the tests.