Moscow: Following their first face-to-face summit in four years, Russian President Vladimir Putin has accepted an invitation from Kim Jong Un to visit North Korea, Al Jazeera reported.

North Korea's Kim is in Russia's Far East as Putin seeks to strengthen ties in the midst of Russia's protracted conflict in Ukraine, in addition to advancing his nation's military modernisation.

After more than four hours of discussions and a visit to the Vostochny Cosmodrome space centre, he extended the offer to Putin at "a convenient time" at a reception to mark the end of the day.

“Putin accepted the invitation with pleasure and reaffirmed his will to invariably carry forward the history and tradition of the Russia-DPRK friendship,” Al Jazeera reported North Korean state news agency KCNA as saying on Thursday.

As a result of the talks in Russia, there is worry not only in the US but also internationally that Kim may be prepared to supply Moscow with weapons for its conflict in Ukraine in exchange for technology that would help him advance his military objectives.

In addition, the North Korean leader is anticipated to go to Vladivostok to see Russia's Pacific fleet and stop by an aviation factory. The director of the nation's weapons department, the defence minister, and the top military commander are all members of Kim's entourage.

The two leaders also agreed to further strengthen strategic and tactical cooperation amid “military threats, provocations and tyranny of imperialists,” Al Jazeera reported citing KCNA.

While speaking to reporters, Putin lauded the "strengthening of cooperation and friendship between our countries" and informed them that he saw "possibilities" for military co-operation with North Korea. Involved in the negotiations was Defence Minister Sergei Shoigu, who in July attended celebrations in Pyongyang honouring the armistice that put a stop to hostilities in the 1950–1953 Korean War on its 70th anniversary.

North Korea launched two short-range ballistic missiles just before Putin and Kim's meeting, the most recent in a series of tests that violated UN sanctions that forbid such actions.

According to US State Department spokesperson Matthew Miller, it is "troubling" that Russia is considering working with North Korea on projects that may go against UN Security Council resolutions.

Yoko Kamikawa, Japan's newly appointed foreign minister, issued a similar caution against "violations" of UN resolutions.

The resolutions, which were supported by Russia, prohibit the development of technologies that might be applied to North Korea's ballistic missile programmes.

Additionally, they forbid any technical and scientific collaboration with North Korea in the fields of nuclear science and engineering, aerospace and aeronautical engineering, or advanced manufacturing production processes, Al Jazeera reported.