Russia's Vladimir Putin and North Korea's Kim Jong Un met for their first-ever summit on Thursday, vowing to seek closer ties as they look to counter US influence.

Putin emerged from the talks saying that like the United States, Russia supports efforts to reduce tensions on the Korean peninsula and prevent nuclear conflicts.

But he insisted that Pyongyang needs guarantees of its security and sovereignty, and took a veiled swipe at Washington for trying to strong-arm North Korea.

"We need to... return to a state where international law, not the law of the strongest, determines the situation in the world," Putin said.

The summit in Russia's Far Eastern city of Vladivostok came with Kim locked in a nuclear stand-off with Washington and Putin keen to put Moscow forward as a player in another global flashpoint.

The two leaders shook hands and shared smiles before heading into one-on-one talks that lasted nearly two hours, longer than expected, at a university campus on an island off the Pacific coast city.

In brief statements before their meeting, both men said they were looking to strengthen ties that date back to the Soviet Union's support for the founder of North Korea, Kim's grandfather Kim Il Sung.

- 'Very meaningful exchange' -

Kim said he hoped to turn the modern relationship with Moscow into a "more stable and sound one" while Putin said the visit would give a boost to diplomatic and economic ties.

Putin said he supported Kim's efforts to normalise relations with the United States and hoped to find out "what Russian can do" to help with the issue of denuclearisation.

The meeting -- which Kim described as "a very meaningful exchange" -- later expanded to include other officials.

About five hours after he arrived, Kim left the campus following a long final handshake with Putin, waving through the window of his black limousine as it drove away.

Putin then addressed reporters alone, saying he would fill in Washington on the results of the talks.

"There are no secrets here, no conspiracies... Chairman Kim himself asked us to inform the American side of our position," said Putin, who was due to fly on to Beijing for another summit.

Kim, who arrived a day earlier in his armoured train, was expected to stay in Vladivostok on Friday for cultural events that Russian media have reported will include a ballet and a visit to the city's aquarium.

The meeting was Kim's first with another head of state since returning from his Hanoi summit with US President Donald Trump, which broke down without a deal on North Korea's nuclear arsenal in February.

It followed repeated invitations from Putin after Kim embarked on a series of diplomatic overtures last year.

Since March 2018, the formerly reclusive North Korean leader has held four meetings with Chinese President Xi Jinping, three with South Korea's Moon Jae-in, two with Trump and one with Vietnam's president.

At the meeting with Trump in Hanoi, the cash-strapped North demanded immediate relief from sanctions, but the talks broke up in disagreement over what Pyongyang was prepared to give up in return.

Russia has already called for the sanctions to be eased, while the US has accused it of trying to help Pyongyang evade some of the measures -- accusations Russia denies.

There were no concrete announcements or agreements, but analysts said Thursday's meeting was valuable to both sides.

"For North Korea, it's all about securing another exit. China talks about sanctions relief but it doesn't really put it into action," said Koo Kab-woo, a professor at the University of North Korean Studies in Seoul.

"For Russia, North Korea is elevating it back to one of the direct parties, on the same footing as China."

- North Korean labourers -

Among the issues that were likely discussed was the fate of some 10,000 North Korean labourers working in Russia and due to leave by the end of this year under sanctions.

Labour is one of North Korea's key exports and sources of cash. Pyongyang has reportedly asked Russia to continue to employ its workers after the deadline.

Moscow was a crucial backer of Pyongyang for decades and their ties go back to the founding of North Korea, when the Soviet Union installed Kim Il Sung as leader.

The USSR reduced funding to the North as it began to seek reconciliation with Seoul in the 1980s, but Pyongyang was hit hard by its demise in 1991.

Soon after his first election as Russian president, Putin sought to normalise relations and met Kim Jong Il -- the current leader's father and predecessor -- three times, including a 2002 meeting also held in Vladivostok.

China has since cemented its role as the isolated North's most important ally, its largest trading partner and crucial fuel supplier, and analysts say Kim could be looking to balance Beijing's influence.

While ties between Moscow and Pyongyang have remained cordial, the last meeting between their leaders came in 2011, when Kim Jong Il told then-president Dmitry Medvedev that he was prepared to renounce nuclear testing.

His son has since overseen by far the country's most powerful blast to date, and launch of missiles which Pyongyang says are capable of reaching the entire US mainland.