North Korea's leader Kim Jong Un (front left) receives a farewell ceremony at the end of his visit to Russia. AFP

North Korea's Kim Jong Un expressed his "heartfelt thanks" to President Vladimir Putin, state media said Monday, as he headed home after nearly a week in Russia on a defence-focused trip.

Kim's tour of Russia's far east, which began Tuesday, has fanned Western fears that isolated, nuclear-armed Pyongyang could provide Moscow with weapons for its war in Ukraine.

During the trip, North Korea's leader inspected everything from Russian space rockets to submarines. It also included a symbolic exchange of rifles with Putin.

Pyongyang's Korean Central News Agency on Monday said Kim "extended his heartfelt thanks to President Putin and the Russian leadership" for "their special care and cordial hospitality" as he wrapped up the visit.

Kim is heading home "after successfully completing the schedule of his official goodwill visit to the Russian Federation," KCNA said.

He also wished "Russia prosperity and its people well-being", the KCNA report added.

North Korea and Russia, historic allies, are both under rafts of global sanctions — Moscow for its Ukraine invasion, Pyongyang for its nuclear weapon tests.

During his visit, Kim said his country would make bilateral ties with Russia its "number one priority", as he held a rare summit with Putin.

China is currently North Korea's most crucial ally and benefactor.

Russia is eager for North Korea's stockpile of artillery shells to be used in Ukraine, while Pyongyang is looking for help with satellite technology and upgrading its Soviet-era military equipment, experts say.

On Wednesday, Putin and Kim held talks at Russia's new Vostochny cosmodrome, roughly 8,000 kilometres (5,000 miles) from Moscow.

After the meeting Putin talked up the prospect of greater cooperation with North Korea and the "possibilities" for military ties.

But the Kremlin has said no agreement has or will be signed.

Agence France-Presse