SEOUL — North Korea launched at least 10 missiles off its east and west coasts on Wednesday, one of which flew near South Korean waters and triggered an air-raid alert on a populated island, where people took cover.
That missile flew southeast over the Northern Limit Line, the inter-Korean maritime border, and fell “close to South Korea’s territorial waters,” according to the South’s military, which called it an unprecedented provocation by the North.
“This is a highly unusual and intolerable act,” Lt. Gen. Kang Shin Chul, the South Korean military’s chief director of operations, said in a statement. “We declare that our military will react in a resolute manner.”
The military issued an air-raid alert on Ulleung, an island off South Korea’s east coast with a population of about 9,000. The missile fell into international waters 103 miles northwest of the island.
“The siren started blaring at 8:55 a.m. and we got a message from our government computer system saying that this is ‘a real-life situation,’” not a mock drill, said Chung Young-hwan, a local official on Ulleung. “We took refuge at an underground shelter for three or four minutes before coming out again.”
Mr. Chung said that the siren was triggered across the island but residents were not immediately told the reason for it. “We knew that it was a North Korean missile when we saw news flashes,” he said.
South Korean defense officials said that they were still studying data to determine the types of missiles North Korea had fired. At least three were ballistic missiles, they said.
Though the North has fired hundreds of rockets and artillery shells into waters not far from the inter-Korean maritime borders in recent weeks, it has rarely launched missiles toward the south.
In 2010, the North shelled a South Korean border island off the country’s west coast, killing four people.
The launch on Tuesday was the most daring missile test by the North since Oct. 4, when it launched an intermediate-range ballistic missile that flew over northern Japan. That missile flew farther than any other missile tested by North Korea.
North Korea has conducted 28 weapons tests this year that involved ballistic and other missiles — more than in any previous year — in defiance of United Nations Security Council resolutions that ban the country from testing ballistic missiles, as well as nuclear devices.
The flurry of missile launches Wednesday came as South Korea was still gripped by shock and mourning over the deaths of more than 150 people in a crowd crush during Halloween festivities in Seoul. President Yoon Suk Yeol’s office said the timing “clearly exposed the true face of the North Korean regime and its flouting of humanity and humanitarianism.”
During a National Security Council meeting on Wednesday, Mr. Yoon said that the North Korean test was “tantamount to violating South Korea’s territorial waters,” his office said. “President Yoon instructed the government to take a stern reaction to ensure that North Korea pays a price for its provocation,” the office said in a statement.
The test also came two days after South Korea and the United States began an annual joint military drill, which this year involved 240 aircraft and thousands of service members from both sides. The allies’ war planes were performing approximately 1,600 sorties, the most ever for the annual drill, as they trained to boost their readiness to deal with the growing missile and nuclear threat from North Korea.
North Korea has called such drills rehearsals for invasion. On Monday, when the exercises began, North Korea protested that the allies’ aircraft were practicing at “striking the strategic targets of the D.P.R.K. in case of contingency in the Korean Peninsula,” referring to the Democratic People’s Republic of Korea, the North’s official name.
“If the U.S. continuously persists in the grave military provocations, the D.P.R.K. will take into account more powerful follow-up measures,” the North’s Foreign Ministry said at the time.