The United States on Friday called on North Korea to refrain from further "provocative" and "destabilizing" actions, and to return to dialogue, after Pyongyang claimed to have tested an underwater nuclear weapons system under development.

The North's defense ministry said the country conducted an "important" test of the Haeil-5-23 system, denouncing this week's naval drills between South Korea, the US and Japan as "reckless confrontation hysteria," according to the Korean Central News Agency.

"We call on the DPRK to refrain from further provocative, destabilizing actions and return to diplomacy," a State Department spokesperson said in response to a question from Yonhap News Agency. DPRK stands for the North's official name, the Democratic People's Republic of Korea.

"In particular, we encourage the DPRK to engage in substantive discussions on identifying ways to manage military risks and create lasting peace on the Korean Peninsula," the official added, reiterating the US harbors no hostile intent toward the North.

Commenting on the North's weapons test, John Kirby, the National Security Council coordinator for strategic communications, said that the US is in contact with South Korea.

"I don't have a lot of specific information. We're not in a position where we can validate those claims," Kirby told a press briefing.

"We're in touch obviously with our South Korean partners to see whatever information context they might have about that. So I can't verify the claims by the North," he added.

Kirby pointed out that if Pyongyang had actually tested the claimed weapon, it underscores the North Korean regime's continued provocations.

"There's little doubt that they continue to pursue advanced military capabilities to threaten their neighbors, to threaten the region," he said.

Regarding the North's hardening rhetoric against Seoul and Washington, Kirby stressed the need to take it "seriously."

"You have to take rhetoric like that seriously from a man in charge of the regime that continues to pursue advanced military capabilities, including nuclear capabilities," he said. "(North Korean leader) Kim Jong-un ought to focus more on feeding his people than on buying and purchasing advanced military capabilities."

Separately, a Pentagon spokesperson reiterated the US' security commitment to South Korea and Japan.

"We have been very clear on the threat posed by the DPRK military programs, and our commitment to the defense of the ROK, Japan, and our commitment to uphold regional peace and stability," the spokesperson said in response to a question from Yonhap News Agency.

"We will continue to work with the both the ROK and Japanese governments to address the threats posed by the DPRK," the official added, noting the US is monitoring North Korean activities. ROK stands for South Korea's official name.

From Monday through Wednesday, South Korea, the US and Japan conducted trilateral naval drills that involved USS Carl Vinson (CVN 70), a Nimitz-class aircraft carrier. The drills followed Pyongyang's latest launch of a hypersonic missile.