In a worrying sign of progress, North Korea fired a suspected missile into the sea on Tuesday for the second time in less than a week, the South Korean military reported.

The early morning launch came as the U.N. Security Council met in New York to discuss last week's test of what Pyongyang called a hypersonic missile, although Seoul has cast doubt on that claim.

But the South Korean military said the "suspected ballistic missile" launched Tuesday had reached hypersonic speeds – a sign of "progress" from the last week's test.

In the decade since leader Kim Jong Un took power, North Korea has seen rapid progress in its military technology at the cost of international sanctions.

Tuesday's missile landed outside Japan's exclusive economic zone. While there were no immediate reports of damage, Japan's Prime Minister Fumio Kishida called the launch "extremely regrettable."

U.S. Forces Korea said the test "highlights the destabilizing impact of the DPRK's illicit weapons program," using the acronym of North Korea's official name.

The missile, fired towards the sea east of the peninsula on Tuesday at around 7:27 a.m. (10:27 p.m. GMT Monday), flew 700 kilometers (435 miles) at an altitude of around 60 kilometers at a speed of Mach 10, South Korea's Joint Chiefs of Staff said.

Hypersonic missiles travel at speeds of Mach 5 and higher and can maneuver mid-flight, making them harder to track and intercept.

Before the U.N. Security Council meeting to discuss Pyongyang's weapons program, six countries, including the U.S. and Japan, called on North Korea to "engage in meaningful dialogue towards our shared goal of complete denuclearization."

Pyongyang had likely planned the latest launch to coincide with the U.N. meeting "to maximize its political impact," Shin Beom-chul, a researcher at the Korea Research Institute for National Strategy, told Agence France-Presse (AFP).

He said the Tuesday launch looked like a hypersonic missile test, judging by the purported speed, but warned against reading too much into it.

"Since South Korea claimed (the Jan. 5 test) wasn't a hypersonic missile referring to the speed, Pyongyang may have tried to showcase its maximum speed," this time around, he said.

Hypersonic missiles were listed among the "top priority" tasks for strategic weapons in its current five-year plan, and it announced its first test – of the Hwasong-8 – in September last year.

Pyongyang has also said it had successfully tested new submarine-launched ballistic missiles, a long-range cruise missile and a train-launched weapon in 2021.

No talks

The new tests come as North Korea has refused to respond to U.S. appeals for talks.

At a key meeting of North Korea's ruling party last month, Kim vowed to continue building up the country's defense capabilities, without mentioning America.

Instead of the policy positions on diplomacy, for which Kim's new year statements are closely watched, he focused on food security and economic development.

Dialogue between Washington and Pyongyang remains stalled and the country is under multiple sets of international sanctions over its nuclear and ballistic missile programs.

The impoverished nation has also been under a rigid self-imposed coronavirus blockade that has hammered its economy.