North Korea fired a barrage of artillery projectiles including short-range ballistic missiles Wednesday, the South Korean military said, with one falling on the south side of the de facto maritime border for the first time since the Korean Peninsula was divided.
A total of 23 missiles were launched from various places, in what a South Korean military source said was a record number fired by North Korea in a single day.
An air raid alarm was sounded around 8:55 a.m. on South Korea's Ulleung Island off the country's east coast, the military said, adding that one missile crossed the Northern Limit Line, a border drawn by U.S.-led U.N. forces after the Korean War.
"It is the first time since the division (of the Korean Peninsula) that a North Korean missile has fallen near South Korean territorial waters," South Korea's Joint Chiefs of Staff said.
The JCS described the missile launches as "unprecedented" and "totally intolerable."
The latest launches by Pyongyang came as a joint air exercise was being conducted by the United States and South Korea.
It was around 6:51 a.m. that the military first detected four unidentified projectiles fired off the west coast from North Pyongan Province area, which later turned out to be short-range ballistic missiles, while three more were launched from Wonsan, Kangwon Province, around 8:51 a.m. off the country's east coast.
According to the military, about 10 missiles, including short-range ballistic missiles and ground-to-air missiles, were additionally confirmed to have been fired off both coasts.
North Korea also fired about 100 artillery projectiles into the maritime buffer zone in the north of the NLL around 1:27 p.m. in violation of a 2018 bilateral military agreement, South Korea said.
The accord was signed when the inter-Korean summit was held between then-South Korean President Moon Jae In and North Korean leader Kim Jong Un.
In response, the South Korean air force fired three air-to-ground missiles toward the north side of the maritime border between 11:10 a.m. and 12:21 p.m., the military said.
"Though one (North Korean) missile crossed the NLL, we fired three missiles to show our willingness (to respond in a determined manner) and capability," a military official said.
Later in the day, six more projectiles, including ground-to-air missiles, were fired from North Korea off the east and west coasts between 4:30 p.m. and 5:10 p.m., the military said, adding that it is maintaining its "readiness posture" against further possible provocations.
President Yoon Suk Yeol held a national security meeting with his top officials in which he ordered that resolute measures be taken to ensure North Korea "pays a price" for its provocation.
Yoon "made it clear that any attempts by North Korea to shake our society and the South Korea-U.S. alliance will not work," the presidential office said in a statement.
In Tokyo, Japanese Prime Minister Fumio Kishida told reporters, "North Korea has been launching missiles at an unprecedented pace, which is totally unacceptable."
The Japanese government said that Pyongyang fired a projectile, possibly a ballistic missile, around 4 p.m., adding that it is believed to have already fallen outside Japan's exclusive economic zone in the Sea of Japan.
The projectile reached a maximum altitude of less than 50 kilometers, and there were no reports of damage to Japanese aircraft or ships, said Senior Vice Defense Minister Toshiro Ino.
Japan lodged a protest with North Korea via its embassy in Beijing, according to the Defense Ministry.
In response to the latest launches, Takehiro Funakoshi, head of the Japanese Foreign Ministry's Asian and Oceanian Affairs Bureau, reaffirmed close cooperation with allies through phone calls with his U.S. and South Korean counterparts Sung Kim and Kim Gunn over boosting deterrence and dealing with the threat of North Korea.
The senior officials also shared "serious concerns over the heightened tensions" on the Korean Peninsula, according to the ministry.
On Monday, the United States and South Korea began their first large-scale joint air exercise in five years. The exercise, to be held through Friday, involves around 240 planes, including F-35 advanced stealth jets.
Prior to the missile launches, North Korea on Tuesday criticized the joint air exercise and warned that the United States and South Korea would "pay the most horrible price in history" if they attempt to use armed force against Pyongyang, according to the official Korean Central News Agency.
Speculation has been growing that the North could conduct its seventh nuclear test and first since September 2017 in the near future.
North Korea has launched ballistic missiles regularly since the start of this year, with one in early October being the first to fly over the Japanese archipelago in five years.
The North fired two short-range ballistic missiles into the Sea of Japan last Friday, marking its 28th round of launches this year if cruise missiles are included.