SEOUL, Oct 1 ― North Korea fired unspecified ballistic missiles toward the east coast today, South Korea's Joint Chiefs of Staff said, marking Pyongyang's fourth launch in a week as it ratchets up tension in the Korean peninsula.

The launch comes after the navies of South Korea, the United States and Japan staged trilateral anti-submarine exercises on Friday for the first time in five years, and follows US Vice President Kamala Harris' visit to South Korea this week.

Japan's coast guard also reported at least two suspected ballistic missile tests by Pyongyang. NHK, citing a government source, said that a second missile had landed outside Japan's exclusive economic zone.

North Korea fired missiles before and after Harris' visit to South Korea, extending a record pace in weapons testing this year as it increases the threat of a credible nuclear power that can strike the United States and its allies.

Pyongyang also conducted the first intercontinental ballistic missile test for the first time since 2017.

Analysts see the increased pace of testing as an effort to build operational weapons, as well as to take advantage of a world distracted by the Ukraine conflict and other crises to “normalise” its tests.

“Despite North Korea’s internal weaknesses and international isolation, it is rapidly modernizing weapons and taking advantage of a world divided by US-China rivalry and Russia’s annexation of more Ukrainian territory,” said Leif-Eric Easley, a professor at Ewha University in Seoul.

“The Kim regime is also playing hardball with the Yoon administration while South Korean politics are hobbled by infighting.”

Nuclear tests and ballistic missile launches by North Korea have long been banned by the Security Council.

The military did not give details of the travel range, height and speed of the missiles.

The isolated country has completed preparations for a nuclear test, a window which could open between China's party congress in October and the US mid-term elections in November, South Korean lawmakers said on Wednesday. ― Reuters