SEOUL: North Korean leader Kim Jong Un was headed home after making a final stop in Russia's far eastern city of Vladivostok, where he visited a university, an aquarium and an animal food plant, state media KCNA reported on Monday.

Kim spent two days in Vladivostok while inspecting various facilities in the fields of military, economy, science, education and culture, before bidding farewell at a send-off ceremony at the Artyom station, KCNA said.

It wrapped up Kim's unusually lengthy, week-long trip to Russia, during which he pledged to step up military and economic cooperation with President Vladimir Putin.

The visit will serve as "an opportunity to further solidify the traditional bond of good-neighbourhood cooperation between the two countries, which are rooted in comradely friendship and military unity, and to open a new chapter in the development of relations," KCNA said.

Kim toured Far Eastern Federal University, where he and Putin held their first talks in 2019, and was briefed by its president on the school's educational system and future development plan.

He also met North Korean students studying science and technology at the university, KCNA said, learning about their lives there and taking a photo together.

At the Maritime Territorial Aquarium, Kim watched white dolphins and other sea animals performing "acrobatic feats," before attending a reception hosted by Alexandr Kozlov, Russia's minister of natural resources and ecology, and visiting the Arnika Bio-Feed Mill.

North Korea's state radio, "Voice of Korea," also reported on Kim's visit to Vladivostok on Monday, saying it "opened a new period of rapid development and strengthening" of bilateral ties and he thanked Putin and other Russian officials for their hospitality.

The rare summit between Kim and Putin has prompted the United States and South Korea to warn against any weapons trade and other military cooperation as Russia presses its invasion of Ukraine and North Korea races to advance its nuclear programmes.

Washington and Seoul officials have expressed concern that Moscow could be seeking to acquire ammunition from the North to prop up its dwindling stocks, while Pyongyang gets technological aid over its spy satellite and missile programmes.

Kim inspected a Russian fighter jet factory that is under Western sanctions, nuclear-capable strategic bombers, hypersonic missiles and warships last week, though Putin has said Moscow would not "violate anything."