SEOUL, South Korea - North Korea said Wednesday it successfully test-fired a strategic cruise missile, part of a selection of recently launched weapons that analysts warn could be destined for Russia's war in Ukraine.

The North's state-run news agency KCNA said the missile, a "Hwasal-2", was fired into the West Sea on Tuesday.

The launch was first noted by Seoul's military, which said it had detected several cruise missiles.

KCNA said the drill was meant to check the army's "rapid counterattack posture" as well as improve "its strategic striking capability".

It added that the launch had "no adverse effect on the security" of neighbouring countries.

This month, Pyongyang has conducted tests of what it called an "underwater nuclear weapon system", a solid-fuelled hypersonic ballistic missile, and a new generation of strategic cruise missiles.

The Hwasal-2 strategic cruise missile has been test-fired before by the North.

Unlike their ballistic counterparts, the testing of cruise missiles is not banned under current UN sanctions on Pyongyang.

Cruise missiles tend to be jet-propelled and fly at a lower altitude than more sophisticated ballistic missiles, making them harder to detect and intercept.

Already on Sunday, North Korea launched from a submarine two Pulhwasal-3-31s, a type of new strategic cruise missile, during a test overseen by leader Kim Jong Un.

Despite rafts of UN sanctions, Seoul and Washington say Kim has been shipping weapons to Russia, possibly in exchange for Moscow's technical assistance in Pyongyang's budding spy satellite programme.

Kim made a rare overseas trip to Russia in September to meet President Vladimir Putin at a cosmodrome, with Putin now set to pay a visit to Pyongyang in return.

The North successfully put its first spy satellite into orbit in November.

"It is believed that North Korea has commenced mass production of cruise missiles ordered by Russia," Ahn Chan-il, a defector-turned-researcher who runs the World Institute for North Korea Studies, told AFP.

The test launches also come as relations between the two Koreas have sharply deteriorated, with Kim declaring Seoul his principal enemy.

In recent weeks, Kim has additionally jettisoned agencies dedicated to reunification and outreach with the South, and threatened war over "even 0.001 mm" of territorial infringement.

Pyongyang's latest launch comes after South Korea conducted a 10-day special forces infiltration drill off the country's east coast, "in light of serious security situations" with the North, which ended on January 25.