- North Korea fired over 200 artillery shells toward a South Korean island.
- Local media said South Korea later fired 400 rounds in a live-fire drill, AP reported.
- South Korea called the incident a "provocative act," North Korea says it was a "natural response."
North Korea launched over 200 rounds of artillery shells off its west coast toward South Korea's Yeonpyeong island between 09:00 to 11:00 local time, said Seoul's military, the BBC reports.
South Korea responded by ordering civilians on the island to seek shelter and conducting live-fire drills as a countermeasure.
Yeonpyeong island, home to a military base and 2,000 people, is a few miles from the North Korean coast. It was a conflict flash point in 2010 when a North Korean artillery barrage killed two soldiers and two civilians.
South Korea retaliated by ordering marines on two border islands to fire artillery shells south of the sea boundary later on Friday, its Defense Ministry said. Local media said South Korea fired 400 rounds, AP reported.
Despite South Korea condemning the action as a "provocative act," North Korea denied that its barrage posed any threat. They did not breach South Korean territory, and all projectiles landed in the buffer zone between the two countries, it said.
South Korea's Joint Chiefs of Staff said that the artillery fire caused "no damage to our people or military" but stressed that such actions "threaten peace on the Korean peninsula and raise tensions," the BBC reported.
Authorities on nearby islands, Baengnyeong and Daecheong, also directed civilians to seek shelter in response to the escalating situation, the BBC reported.
Prepare 'for a great event'
Tension along the Korean Demilitarized Zone has been mounting.
Last week, the Korean Central News Agency (KCNA), the state news agency of North Korea, leader Kim Jong Un will "no longer seek reconciliation and reunification" with South Korea, per CNN.
He added that the Communist state's armed forces should prepare "for a great event to suppress the whole territory of South Korea," per the Financial Times.
South Korea's Defense Minister Shin Won-sik said it had to amp up military readiness to deter further provocations.
The KCNA justified its firing drills as a "natural response" to a weeklong US-South Korean military exercises involved thousands of troops, artillery, tanks, armored vehicles, and warplanes.
The cooling of relations began when Pyongyang said it launched a spy satellite into space in November, prompting South Korea to resume surveillance flights along the border.
US National Security Council spokesperson Adrienne Watson said Washington condemned the satellite launch, saying it "raises tensions and risks destabilizing the security situation in the region and beyond." She said it involved technologies directly related to North Korea's intercontinental ballistic missile program, AP reported.
North Korea claims it will launch three more spy satellites in 2024, according to reports.
The Korean War, which divided the peninsula into North and South Korea, ended in 1953 with an armistice. The two countries remain technically at war.