WASHINGTON

The UN is "very concerned" about North Korea's test of its underwater nuclear weapons system in response to this week's joint military drills by South Korea, the US and Japan, a UN spokesman said on Friday.

"We have seen this development and we remain concerned and very concerned about the current situation on the Korean Peninsula," Stephane Dujarric told reporters.

His remarks came after North Korea's Defense Ministry said it carried out "an important test of its underwater nuclear weapon system ‘Haeil-5-23’ under development" in the East Sea.

"The Secretary-General (Antonio Guterres) reiterates his call for de-escalation, the full implementation of Security Council resolutions and for the creation of environment that is conducive to dialogue and the resumption of diplomatic talks which are frankly the only possible path forward," Dujarric said.

The trilateral maritime exercise by Seoul, Washington, and Tokyo included the US nuclear carrier USS Carl Vinson and the Aegis-guided missile cruiser USS Princeton.

Pyongyang said the joint drill “constituted a cause of further destabilizing the regional situation, and they are an act of seriously threatening the security” of North Korea.