North Korea's leader, Kim Jong Un, has met the families of soldiers killed fighting for Russia against Ukraine and expressed his 'deep condolences', state media says.

In a special ceremony held on Friday, Kim was seen comforting bereaved families and presenting them portraits of their dead loved ones wrapped in the North Korean flag.

South Korea believes the North has sent some 15,000 troops to aid Russia's war with Ukraine, along with missiles and long-range weapons. In return, North Korea is believed to have received food, money, and technical help.

North Korea only acknowledged its role in the foreign conflict in April, admitting that some of its soldiers had been killed.

In January, Western officials told the BBC they believed at least 1,000 of the troops sent from North Korea had been killed in three months, with several thousand more wounded. However, recent estimates have put the figure closer to 600 killed.

Friday's ceremony was the second of its kind in a week. During the event, Kim stated he was filled with 'sorrow' at failing to bring the soldiers back alive and pledged to build a monument in their honour and to care for their children.

'I thought a lot about other martyrs' families who were not present [at the previous ceremony]. So, I had this meeting arranged as I wanted to meet and console the bereaved families of all the heroes and relieve them of their sorrow and anguish even a little,' KCNA reported Kim as saying.

Kim is due to meet Russia's Vladimir Putin in China next week, attending a military parade marking Japan's surrender in World War II. This will be their third meeting in two years, at a time when Moscow and Pyongyang are deepening their cooperation, and relations between both countries have reached a new level.

Last October, Kim sent a birthday message to Vladimir Putin, calling him his closest comrade. That same month, Putin introduced a bill to ratify a military pact he made with Kim, which promises mutual support in case of 'aggression' against either country.

North Korea has about 1.28 million active soldiers, but its army had no recent experience of combat operations overseas until the deployment to Ukraine.