For years, North Korea has been under a sprawling, complex network of UN sanctions over its banned nuclear and ballistic missile weapons programmes, with violations carefully tracked and monitored by experts.

But with one veto, Russia has put a stop to much of this work -- not lifting the sanctions but ending the UN's monitoring, a major win for North Korea's Kim Jong Un, according to experts.

AFP takes a look at what we know:

 What happened?

 After North Korea tested a second nuclear weapon in 2009 and UN sanctions were imposed on Pyongyang, a panel of experts was set up -- with support from Russia and China -- to monitor and report on any sanctions-violating activities.

The panel's mandate expires annually at the end of April, and this year Russia blocked its renewal. Weeks before, the panel said it was investigating reports of arms transfers between Moscow and Pyongyang.

Pyongyang has shipped significant quantities of weapons to Russia for use in Ukraine, Seoul and Washington claim.

Russia's veto is "almost comparable to destroying a CCTV to avoid being caught red-handed", Hwang Joon-kook, Seoul's UN ambassador, said.

 Why did Russia veto?

 Russia claims the body was not doing its job.

The panel's "work is increasingly being reduced to playing into the hands of Western approaches", Moscow's UN ambassador Vassily Nebenzia said, accusing it of "reprinting biased information".

Moscow has drawn closer to Pyongyang in recent years, particularly since Russia was placed under Western sanctions for its invasion of Ukraine.

"Russia has revealed its opposition to sanctions against its own country through North Korea," Hong Min, a senior analyst at the Korea Institute for National Unification, told AFP.

 What about China?

 Beijing, long Pyongyang's most important ally, abstained from the vote rather than joining Russia in vetoing.

"A political solution is the only way," Chinese foreign ministry spokesperson Lin Jian said Friday in explaining the abstention.

"The current situation on the (Korean) Peninsula remains tense, and blindly imposing sanctions cannot solve the issue," he said.

China has supported easing sanctions on the North, and prior to the vote, had backed Russian proposals to introduce so-called sunset clauses on them and reduce the frequency of panel reports.

But "to Beijing’s dismay, trilateral cooperation among Washington, Seoul and Tokyo may actually increase" due to the panel's demise as the allies seek to counter Pyongyang, said Leif-Eric Easley, a professor at Ewha University in Seoul.

In addition, "more evidence of sanctions violations could be released to the public since the restraining influence Russia and China had over headline-generating reports will be gone with the UN panel," he said.

 What will change?

 Sanctions on the North are becoming increasingly ineffective, experts say, thanks largely to Russia and China.

As global rivalries heated up, since around 2019, Moscow and Beijing began lobbying for sanctions relief at the United Nations.

At the time, Russia "used North Korea as leverage to protest NATO's eastward expansion in Europe and the strengthening of US forces in the Western Pacific," the Korea Institute for National Unification's Hong said.

Former US President Donald Trump -- who had historic but ultimately failed meetings with the North's leader Kim Jong Un -- also employed aggressive anti-Beijing rhetoric during his time in office.

The only significance of Thursday's veto was that "finally the real position of Russia (and China) towards the Panel and the wider sanctions regime has been made clear," said Eric Penton-Voak, who was coordinator of the panel until last year.

"The only real surprise to those who follow this issue is that this didn't happen earlier," he told Seoul-based specialist site NK News.

Recently, Pyongyang has moved to take advantage of gridlock at the United Nations, ramping up missile tests and weapons development and declaring itself an "irreversible" nuclear power in 2022.

If Washington wants to change this trajectory, "cooperation from China and Russia, which have the most interactions with North Korea, is crucial," Yang Moo-jin, president of the University of North Korean Studies in Seoul, told AFP.

 And Russia-North Korea ties?

 Kim met Russian President Vladimir Putin in September last year, with Pyongyang's leader declaring Moscow ties his country's "number one priority".

The two countries have subsequently stepped up cooperation, with Seoul claiming earlier this month that the North has now sent 7,000 containers of arms to Russia for its war with Ukraine.

North Korea's border remains largely closed due to pandemic-era restrictions, but a group of Russian tourists visited Pyongyang last month -- the first known foreign tour group since Covid. Moscow's spy chief visited this week, the official Korean Central News Agency said.

Russia's veto marks a real victory for Kim Jong Un, Patrick Cronin, Asia-Pacific security chair at the Hudson Institute, told the Yonhap News Agency.

"Kim Jong Un's Kremlin courtship pays off. Pyongyang wants to end sanctions without slowing its strategic weapons programs," he said.