North Korea fired two more ballistic missiles this week, South Korea s military said, its fourth such launch this week, as Seoul, Tokyo and Washington ramp up joint military drills.
The US vice-president, Kamala Harris, visited the region this week after South Korea, the United States and Japan staged trilateral anti-submarine exercises on Friday for the first time in five years.
Harris was on Thursday in Seoul and toured the heavily fortified demilitarised zone that divides the peninsula, in a trip that aimed to underscore her country's ironclad commitment to South Korea's defence against the North.
Pyongyang has doubled down on its banned weapons programmes this year, revising its laws to declare itself an irreversible nuclear power, and conducting a record-breaking blitz of tests this year.
South Korea's military said it had detected two short-range missiles between 0645 and 0703 fired from the Sunan area in Pyongyang into the East Sea, referring to the body of water known as the Sea of Japan.
The missiles flew around 350 km at an altitude of 30 km at the speed of Mach 6 Seoul s joint chiefs of staff said the launches were a serious provocation and that the missiles had landed outside Japan's exclusive economic zones.
Toshiro Ino, Japan's vice defence minister, said the missiles appear to have flown in irregular trajectories. Experts say the irregular trajectories indicate the missiles are capable of manoeuvring in flight, making them harder to track and intercept.
The US Indo-Pacific Command stated in a statement that the latest launch highlights the destabilising impact of the DPRK's illegal WMD and ballistic missile programs using the official abbreviation for North Korea.
On Sunday, Wednesday and Thursday, Harris visited Seoul with a flurry of missile launches firing off short-range ballistic missiles, including a few hours after the vice-president flew out of South Korea.
Washington has about 28,500 troops stationed in South Korea to protect it from the North.
Under the leadership of Seoul spokesman Yoon Suk-yeol, who took office in May, the two countries have boosted joint exercises that they insist are purely defensive.
Just before Harris arrived in Seoul, Washington sent the nuclear-powered USS Ronald Reagan aircraft carrier to South Korea to conduct a large-scale joint naval exercise.
Such drills infuriate North Korea, which sees them as rehearsals for an invasion.
Leif-Eric Easley, professor at Ewha University in Seoul, said that North Korea was rapidly modernising weapons and taking advantage of a world divided by US-China rivalry and Russia annexation of more Ukrainian territory, but he said that the short-range ballistic tests are less important than a nuclear test but still violate UN Security Council resolutions.
South Korean and US officials have warned for months that the North Korean ruler, Kim Jong-un, is preparing to conduct another nuclear test.
The South s spy agency said on Wednesday that North Korea's next nuclear test could happen in the window between China's upcoming party congress on 16 October and the US midterm elections on 7 November.
North Korea, which is subject to UN sanctions for its weapons programmes, typically seeks to maximize the geopolitical impact of its tests with careful timing.
The isolated regime has tested nuclear weapons six times since 2006, most recently in 2017.