North Korea's Foreign Minister Choi Sun-hui issued a statement condemning the sanctions regime after South Korea, the US and Japan on Thursday announced the launch of the monitoring mechanism with eight other countries after Russia's veto ended a UN monitoring panel's mandate in April, Yonhap news agency reported.
The other countries are France, the UK, Germany, Italy, the Netherlands, Canada, Australia and New Zealand.
Choi said the monitoring team is "unlawful and illegitimate" and constitutes "a denial of the UN Charter", according to the English-language statement carried by the Korean Central News Agency (KCNA).
"The forces involved in the smear campaign against the DPRK will have to pay a dear price for it," Choi said, referring to North Korea's official name, the Democratic People's Republic of Korea.
Choi also criticised the US for pursuing its "hegemonic interests" and warned of "inevitable reactions" in response to what she described as a violation of North Korea's sovereignty.
The monitoring team is expected to monitor and report violations of UN sanctions, which are designed to prevent Pyongyang from advancing its nuclear and missile programmes.
North Korea has been accused of evading these sanctions through methods such as ship-to-ship transfers, with alleged support from countries like China and Russia.