North Korean leader Kim Jong Un called for building a strong, modern army to cope with any war during a visit to a military academy, state media KCNA said on Wednesday.

Kim's trip to the Kang Kon Military Academy comes after North Korea has sent thousands of troops to Russia to support its war against Ukraine. This week Kim also visited the Kim Il Sung University of Politics, another elite cadre training institution, calling for military loyalty and sacrifice.

South Korea's intelligence agency has said Kim's previous inspections of military units and training might be part of preparations for an additional dispatch of soldiers to Russia.

During the latest visit to the military academy, Kim criticised the school's poor management and operation of educational facilities, saying it failed to meet the ruling party's pursuit of "modernity and advanced character" in building a powerful army, KCNA said.

He laid out tasks to refurbish the facilities and intensify education focusing on practice so that the students would learn about the "actual experiences of modern warfare", and to master advanced weapons and technical equipment, it said.

"The present international situation, in which the aggressive and bellicose nature of the imperialists is most openly expressed in history and war and bloodshed become commonplaces, requires the armed forces ... to perfectly cope with a war," Kim said, according to KCNA. South Korean officials have warned that North Korea could benefit from supplying weapons and troops to fight in Russia by gaining experience and insight from operating on a modern battlefield.

Kyiv has said North Korean forces have suffered heavy casualties in Russia, with more than 3,000 soldiers killed or wounded by early January this year.