Russia has shut down a panel of UN experts that have for years monitored sanctions against North Korea.
The panel last week said it was probing reports that Russia violated rules by buying North Korean weapons like ballistic missiles for use in Ukraine.
The UN`s Security Council has imposed a series of sanctions on Pyongyang since 2006 for its nuclear weapons programme.
Those restrictions are still in force - but the experts group set up to monitor violations will now be disbanded.
In a Security Council vote on Thursday, Russia used its veto power as a permanent member to block the renewal, while 13 of the other 14 member states present voted for it. China, Pyongyang`s closest ally, abstained.
Russia`s block triggered a wave of condemnation from the US, UK, South Korea and other Western allies and comes after a year of high-profile public meetings between Moscow and Pyongyang leaders.
This is the first time Russia has blocked the panel - which has been renewed annually by the UN Security Council for 14 years.
Ukraine`s Foreign Minister Dmytro Kuleba said on social media Russia`s veto was tantamount to "a guilty plea" that it was using North Korean weapons in the war.
The US, UK and France all told the Council that Russia was silencing the watchdog because it had begun to report on Moscow`s own violations of the rules- specifically purchasing weapons from North Korea for the battlegrounds in Ukraine.
Meanwhile, South Korea`s representative at the UN criticised Russia`s "blind self-centeredness" and said it had no justification "for disbanding the guardians" of the sanctions regime.
"This is almost comparable to destroying a CCTV to avoid being caught red-handed," Ambassador Hwang Joon-kook said.
Russia has consistently denied using North Korean weapons and its representative at the UN again dismissed the accusations on Thursday.
Vasily Nebenzia also argued that the panel of experts had no added value.
"The panel has continued to focus on trivial matters that are not commensurate with the problems facing the peninsula," said Mr Nebenzia, who also added that sanctions had imposed a "heavy burden" on the North Korean people.
Since 2019, Russia and China have sought to persuade the Security Council to ease sanctions.
The Security Council first imposed sanctions in 2006 in response to a North Korean nuclear test, and has since passed 10 more resolutions strengthening them as Pyongyang`s nuclear activity has continued.
However Kim Jong Un`s regime has largely ignored the sanctions- despite their impact on the economy. The North Korean leader has rapidly continued nuclear weapons development and has pursued a more aggressive and dangerous military strategy in recent years.
The UN experts say North Korea continues to flout sanctions through increased missile test launches and developing nuclear weapons. The regime launched a spy satellite this year - with technology believed to have been provided by Russia.
In breach of the sanctions, it also continues to import refined petroleum products and send workers overseas, and the UN panel`s most recent report detailed a campaign of cyber attacks.