Russian President Vladimir Putin on Wednesday said North Korea had hosted children of Russian soldiers killed in Ukraine at a summer camp in the reclusive country.

Putin thanked North Korean leader Kim Jong Un for the "act of care" during a state visit to Pyongyang to advance Russia's relations with its closed neighbour as ties with Western countries are ruptured over Ukraine.

The Russian children, who were sent to the Songdowon International Children's Camp on the Pacific coast, are rare outsiders in the country which shut itself off from the world even more after the Covid pandemic.

"I want to thank our Korean friends and personally comrade Kim Jong Un for organising the holiday of the children of killed participants of the special military operation in the Korean camp Songdowon," Putin said, using Moscow's term for its offensive on Ukraine.

"We highly value this genuine act of care and friendship," he added.

Moscow has not said how many of its troops have been killed in more than two years of fighting in Ukraine, but the number is believed to be at least in the tens of thousands.

Putin said that the countries were developing tourism ties.

"For the summer season, tours are being organised, focused on holidaying in Korean seaside resorts," he said.

Russia and North Korea share a short land border, near the city of Vladivostok.

As Moscow touts relations with Pyongyang, regional authorities in the Russian Primorye region bordering North Korea have also upped cooperation.

Local governor Oleg Kozhemyako touted sending children from the region to North Korean camps during a visit by Kim to Russia's Far East last year, causing some alarm from parents.

In an address to schoolchildren, Kozhemyako said: "When we were like you, we would go there, they had good camps in Korea. That's why maybe we will agree and send some (children) to pioneer camps... There is the sea there and it is warm."

In April, he said some 200 school children were ready to holiday in Songdowon.

At the time, the head of the Russian League for a Safe Internet, Yekaterina Mizulina, said she was flooded with complaints from concerned local parents.