North Korea said on Thursday it had successfully test-fired a new submarine-launched ballistic missile (SLBM) from the sea to contain external threats and bolster self-defence, ahead of fresh nuclear talks with the United States.

The launch on Wednesday was the most provocative by North Korea since it resumed dialogue with the United States in 2018 and a reminder by Pyongyang of the weapons capability it has been aggressively developing, including intercontinental ballistic missiles, analysts said.

North Korean leader Kim Jong Un “sent warm congratulations” to the defence scientists who conducted the test, state news agency KCNA said, indicating he did not attend the launch as he has at previous tests of new weapons systems.

The new type of SLBM, called Pukguksong-3, was “fired in vertical mode” in the waters off the eastern city of Wonsan, KCNA said, confirming an assessment by South Korea’s military on Wednesday that the missile was launched on a lofted trajectory.

“The successful new-type SLBM test-firing comes to be of great significance as it ushered in a new phase in containing the outside forces’ threat to the DPRK and further bolstering its military muscle for self-defence,” KCNA said.

DPRK is short for the North’s official name, the Democratic People’s Republic of Korea.

The test “had no adverse impact on the security of neighbouring countries,” KCNA said but gave no other details about the launch.

Photos released in the North’s official Rodong Sinmun newspaper, whose front two pages featured the test, showed a black-and-white painted missile clearing the surface of the water, then the rocket engine igniting to propel it into the sky.

A State Department spokeswoman called on Pyongyang to “refrain from provocations” and to remain committed to nuclear negotiations.

South Korea expressed strong concern and Japanese Prime Minister Shinzo Abe condemned the launch, saying it was a violation of UN Security Council resolutions.

North Korea rejects UN Security Council resolutions that ban Pyongyang from using ballistic missile technology, saying they are an infringement of its right to self-defence.

Talks aimed at dismantling North Korea’s nuclear and missile programs have been stalled since a second summit between Kim and US President Donald Trump in Vietnam in February broke down in disagreement over nuclear disarmament.

North Korea fired the missile hours after announcing it would resume talks with the United States by holding working-level negotiations on Oct. 5.

North Korea’s chief nuclear negotiator, Kim Myong Gil, arrived at the Beijing airport on Thursday with other North Korean officials and booked flights to Stockholm, Sweden, Yonhap reported, citing an airport official.

“We’re going for the DPRK-US working-level negotiations,” the negotiator Kim told reporters in Beijing, according to Yonhap. “There’s been a new signal from the U.S. side, so we’re going with great expectations and optimism about the outcome.”

‘NUCLEAR CAPABLE’

The Pukguksong-3 appeared to be a new design that has enhanced range and stability compared with a version tested in 2016, three analysts said.

It was probably launched from a test platform and not a submarine, which would be the final stage of testing, said Kim Dong-yub, a military expert at Kyungnam University’s Institute of Far Eastern Studies in Seoul.

State news agency KCNA released photos and a report in July of leader Kim Jong Un inspecting a large, newly built submarine, but an unnamed South Korean military source said on Thursday that the submarine appears to be still incomplete, Yonhap news agency reported.

Leader Kim Jong Un’s absence at the test is “extremely unusual,” Kyungnam University’s Kim said, probably meant to contain the political fallout that could result in the upcoming talks falling apart before they even start.

On Wednesday, South Korea’s military said the missile flew 450 km (280 miles) and reached an altitude of 910 km (565 miles). It was likely a Pukguksong-class weapon, as the North’s earlier submarine-launched ballistic missiles (SLBMs) under development were known.

South Korean Defence Minister Jeong Kyeong-doo said the Pukguksong, or Pole Star in Korean, would have had a range of about 1,300 km (910 miles) on a standard trajectory.

North Korea had been developing SLBM technology before it suspended long-range missile and nuclear tests and began talks with the United States that led to the first summit between Kim and Trump in Singapore in June 2018.