North Korean missile lands closer than before to South's waters for the 'first time ever': Seoul

North Korea fired at least 10 missiles on Wednesday, including one that landed close to South Korea's territorial waters and prompted a rare warning for people on an island to shelter in bunkers.

"The North Korean missile launch is very unusual and unacceptable as it fell close to South Korean territorial waters south of the Northern Limit Line for the first time" since the peninsula was divided, Kang Shin Chul, Director of Operations for the Joint Chiefs of Staff (JCS) told reporters.

An air raid warning was issued for the island of Ulleungdo, JCS said, which was flashed on national television. Its residents were instructed to "evacuate to the nearest underground shelter".

"We declare that our military will respond decisively to this," he added.

In a statement, the JCS described the missile launch near South Korean territorial waters as very rare and intolerable".

"Our military vowed to respond firmly to this [provocation]," it added.

The JCS had initially said it detected the launch of three short range ballistic missiles, but later announced North Korea had fired "at least 10 missiles of various types today towards the east and west".

South Korean President Yoon Suk Yeol called a meeting of the National Security Council over the launch, ordering "swift and stern measures, so that North Korea's provocations pay a clear price".

Japan also confirmed the North Korean missile launches, with Prime Minister Fumio Kishida telling reporters that he planned to call a "national security meeting as soon as possible".

Pyongyang's latest launch comes as Seoul and Washington stage their largest-ever joint air drills, dubbed "Vigilant Storm", which involve hundreds of warplanes from both sides.

Pak Jong Chon, a high-ranking official in North Korea, said the drills were aggressive and provocative, according to a report in state media on Wednesday.

"If the US and South Korea attempt to use armed forces against the (Democratic People's Republic of Korea) without any fear, the special means of the DPRK's armed forces will carry out their strategic mission without delay," he said.

"The US and South Korea will have to face a terrible case and pay the most horrible price in history."

One of the missiles on Wednesday landed in waters just 57km east of the South Korean mainland, the military said.

"In protest of the joint US-South Korea drill, Pyongyang seems to have staged the most aggressive and threatening armed demonstration against the South since 2010," Cheong Seong Chang, a researcher at the Sejong Institute told AFP.

In March 2010, a North Korean submarine torpedoed the South Korean naval vessel Cheonan, killing 46 sailors, including 16 who were on their mandatory military service.