The U.N. Security Council meets on Ukraine, at U.N. headquarters in New York City on Jan. 10. AFP-Yonhap

The U.N. Security Council (UNSC) held closed-door consultations on North Korea-related issues on Thursday, sources said, amid tensions heightened by Pyongyang's recent launch of a claimed hypersonic missile and its hardening rhetoric against Seoul.

The informal UNSC meeting came as South Korea began its two-year term as a non-permanent member this month. Seoul, Washington and Tokyo are said to have requested the meeting — this year's first UNSC consultations dedicated to North Korean issues.

The North launched what it claims was a solid-fuel intermediate-range ballistic missile tipped with a hypersonic warhead on Sunday. Later, it ratcheted up tensions by mentioning South Korea as the "invariable principal enemy."

"In-depth consultations took place," South Korean Ambassador to the U.N. Hwang Joon-kook told reporters. "Taking together North Korea's rhetoric and its action, the situation has gotten more serious, and all (UNSC) members are very concerned with respect to that."

At the meeting, South Korea reportedly noted changes in Pyongyang's nuclear policy and highlighted the need to pay attention to all kinds of North Korean threats undermining global peace -- in a departure from the UNSC's focus on the North's long-range ballistic missile launches.

Earlier this month, Hwang said that South Korea will directly request a UNSC meeting in the event of a North Korean provocation if needed, as its UNSC term started this month. (Yonhap)