Vladimir Putin and Kim Jong Un have signed an agreement pledging that Russia and North Korea will help each other in the event of "aggression" against either country.

The Russian president made the announcement following talks with Mr Kim during a lavish visit to Pyongyang, his first since 2000.

Mr Kim said it took their relationship to "a new, high level of alliance".

The pact cements a rapidly blossoming partnership that has worried the West. It could also have significant ramifications for the world, say observers.

Any kind of mutual defence treaty could possibly see Moscow assisting Pyongyang in a future conflict on the Korean peninsula, while North Korea could openly help Russia in its war on Ukraine.

Mr Kim is already accused of supplying Russia with weapons, while Mr Putin is thought to be giving the North Koreans space technology that could aid their missile programme. The two last met in Russia in September.

On Wednesday they signed a "comprehensive partnership agreement" that included a clause where they agreed to provide "mutual assistance in the event of aggression" against either country, said Mr Putin. He did not spell out what would constitute aggression.

Mr Putin has in recent months faced difficulties on the battlefield in Ukraine, particularly with depleting weapons. During their last face-to-face meeting in September, when Mr Kim visited Russia, the two had discussed military cooperation and were suspected of striking an arms deal. Since then there has been growing evidence that Russia has been deploying North Korean missiles in Ukraine.

In the last few weeks however, the US and other Nato countries have given permission to Ukraine to use Western weapons on Russian soil, in a significant move that Kyiv hopes would turn the tide to its favour.

Mr Putin warned of consequences and earlier this month said he was considering arming adversaries of the West with long-range weapons - something that North Korea has been developing.

He criticised the West's decision again on Wednesday, saying it was "a gross violation" of restrictions under international obligations.

He also took issue with Western sanctions on Russia and North Korea, saying that they both "do not tolerate the language of blackmail and diktat" and would continue to counter the West's use of "sanctions strangling" to maintain "hegemony".

Mr Kim meanwhile praised their treaty as marking a significant and historic moment in their relation. He also expressed "full support and solidarity" for Russia in its war on Ukraine.

The treaty is likely to anger Seoul, which had ahead of the meeting warned Russia against going “beyond a certain point”.

National Security adviser Chang Ho-jin had told his Russian counterpart that Moscow "should take into consideration which among North Korea and South Korea will be more important to it, once Russia ends its war with Ukraine”.

Rachel Lee, a senior fellow at the Stimson Center think tank's Korea programme, said any such treaty would have "significant implications for the region and the world".

Besides the possibility of Russian intervention in a fresh conflict between the two Koreas, "if North Korea continues to supply weapons to Russia, and Russia provides advanced military technology to North Korea, we can face an even greater global [weapons] proliferation problem."

Chad O’Carroll, a North Korean specialist from NK News, said on X, formerly Twitter, that the clause could open the door to conflict-related co-operation, including the possibility of North Korean soldiers assisting Russia in Ukraine.

Mr Putin's visit kicked off with a later than expected arrival in Pyongyang which saw him touch down at about 0300 local time (18:00 GMT). Once he stepped off the plane, Mr Kim greeted him with an embrace and a red carpet welcome where apparently no expense was spared.

As the Russian leader was ferried to the Kumsusan guesthouse, the same place where fellow ally Chinese president Xi Jinping stayed previously, North Korean state media showed the capital ablaze with light from streetlamps and buildings. It was a striking image for an impoverished country suffering from a chronic electricity shortage.

At the welcoming ceremony later on Wednesday, Mr Putin was greeted by a spectacle of enthusiastic devotion choreographed to its minutest detail and rife with North Korean propaganda imagery. Typical of the North Korean regime, it featured a cast of hundreds of thousands, many of whom would have been told to participate.

Accompanied by police on motorbikes riding in perfect formation, his motorcade glided through the streets of Pyongyang lined with people waving Russian flags, bouquets of flowers and pictures of Mr Putin. They chanted "welcome Putin" and "North Korea Russia friendship".

At Kim Il Sung Square, named after the regime's founder and Mr Kim's grandfather, a crowd dressed in the two countries' flag colours and evenly spaced out on the square waited for Mr Putin's arrival. As he stepped out of his car, they cheered and released balloons into the sky.

Little children dressed in white, the colour symbolising the purity of North Korean society, greeted the Russian leader. Mr Putin and Mr Kim walked past rows of soldiers mounted on white stallions - a nod to the horse Mr Kim's grandfather was said to have ridden while leading his army against the Japanese.

The two men then surveyed goose-stepping soldiers while standing in front of solemn, metres-tall portraits of themselves which adorned a nearby building and loomed over the festivities below.

Later, Mr Putin attended a gala concert and state reception with banquet, where the menu featured dishes such as cod in the shape of a white flower, Korean noodles and chicken soup with ginseng and pumpkin.

The festivities ended with Mr Putin flying off late on Wednesday for Vietnam, but not before the two exchanged gifts. Mr Putin gave Mr Kim a second luxury Aurus car - and even took him for a spin in it. The first was presented to Mr Kim during his visit to Russia. He also gave Mr Kim a ceremonial admiral's dagger and a tea set. In return Mr Kim gave several works of art said to feature Mr Putin's likeness.

Mr Putin was last in Pyongyang in 2000, just four months after he took power, to meet Mr Kim's father Kim Jong Il.

Twenty-four years later, North Korea's economy has been crippled even further by international sanctions. Many observers believe Kim Jong Un requested crucial aid such as food, fuel, foreign currency and technology from North Korea's old friend. In Soviet times, Russia played an instrumental role in propping up the Kim family regime.

During Mr Kim's visit to Russia last September, Mr Putin had promised to help North Korea develop its satellites, after several failed launches. The US believes North Korea's satellite programme is also aimed at boosting its ballistic missile capabilities, as the technology is similar.

But both leader also stand to reap diplomatic gains and soft power, note observers.

They "trying to reduce the pain of international sanctions by creating an alternate network of friends and partners beyond the reach of US sanctions," noted Jeffrey Lewis, a director at the James Martin Center for Nonproliferation Studies.

This in turn bolsters the "multipolar" world view that Russia, China and other states have been pushing as an alternative to the current international order led by the US and Western allies, say analysts.

Additional reporting by Joel Guinto, Kelly Ng and Jake Kwon.