North Korea fired multiple cruise missiles off its east coast on Sunday, its second such launch in less than a week, South Korea's Joint Chiefs of Staff (JCS) said.
The missiles were launched at around 8am local time and were being analysed by South Korean and US intelligence authorities, the JCS said, without specifying how many missiles were fired or how far they travelled.
"While strengthening surveillance and vigilance, our military is co-operating closely with the United States and monitoring additional signs and activities from North Korea," it said in a statement.
The latest launches came days after North Korea fired what it called a new strategic cruise missile called "Pulhwasal-3-31", suggesting it is nuclear capable.
North Korea is stepping up confrontation with the US and its allies, but officials in Washington and Seoul say they have seen no signs Pyongyang intends to take imminent military action.
Tensions on the Korean Peninsula have increased in recent months as Kim Jong-un continues to accelerate his weapons development and issue threats of nuclear conflict with the US and its Asian allies.
Earlier this month the UN condemned ballistic missile transfers from Russia to Pyongyang.
North Korea has been under a UN arms embargo since it first tested a nuclear bomb in 2006.
“Each violation makes the world a much more dangerous place,” read the joint statement by permanent Security Council members Britain, France and the US, non-permanent members Malta, Slovenia and South Korea, as well as Japan and Ukraine.
The US, South Korea and Japan have been expanding their combined military exercises in response to the increased launches, which Kim portrays as invasion rehearsals, and sharpening their deterrence strategies built around nuclear-capable US assets.
North Korea’s cruise missiles supplement the country’s huge line-up of ballistic missiles, including intercontinental ballistic missiles designed to reach the US mainland.
South Korea’s representative to the UN, Hwang Joon-kook, has said North Korean missiles have also been used by Russia in its war in Ukraine.
Washington has also found evidence North Korean weapons have been used against Ukrainian civilians, and said Pyongyang also hopes to secure arms from Iran.
