Shots fired across the border between the two Koreas have continued to strain already tense relations. The two countries continue a standoff that has last more than half a century and that endangers the whole region.

According to Reuters, North Korea fired an artillery shot at a South Korean navy patrol ship that was patrolling along the southern side of the boundary shared by the two nations. The shell did not hit the ship, according to a South Korean military official.

The Northern Limit Line was drawn up after the end of the Korean War and has been the de-facto boundary between the communist north and the capitalist south. North Korea, however, does not recognize the boundary and continues to taunt its southern neighbor by holding military games near it.

Reuters reports that residents of Yeonpyeong island were evacuated to bomb shelters when the incident occurred since the island sits right below the line, and in 2010 North Korean shells landed on the area, killing residents.

Firing stopped by 6 p.m. local time; however, that was not before South Korea retaliated by firing at a North Korean ship. Reuters reports that both nations have been at odds since South Korean vessels fired warning shots at North Korean patrol ships breaching the borderline. As a result, North Korea threatened to "blow up" any South Korean navy ship near the border.

North Korea claims it was patrolling for illegal Chinese fishing boats on the first incident, according to Yonhap News Agency. However, South Korea's military remains steadfast on its decision.

"North Korea has continued provocative actions such as an illegal intrusion into the NLL, and repeated absurd threats to us by branding our normal maritime guard operations as a military provocation," the South's Navy Second Fleet said in a statement.

South Korea has vowed to launch a "merciless counterattack" against any North Korean incursions.