The three-day meeting of the North Korean central committee discussed key policy issues as well as plans for an upcoming congress of its ruling party -- North Korea's first in five years and expected next month.

Wrapping up the meeting on Thursday, Kim condemned "the wrong ideological viewpoint and inactive and irresponsible work attitude" of some officials, the state-run Korean Central News Agency (KCNA) said.

He called on officials to have "greater confidence in and courage for the future of our cause and struggle".

He also "pointed out the shortcomings and evil practices that must be corrected", KCNA said.

State media did not offer any specifics, though it did say the ruling party had revealed numerous recent "deviations" in discipline -- a euphemism for corruption.

The North Korean leader reserved praise for Pyongyang's soldiers fighting against Ukraine alongside Russia, of whom at least 600 have died and thousands more sustained wounds, according to South Korean estimates.

Their work, Kim said, "demonstrated to the world the prestige of our army and state as the ever-victorious army and genuine protector of international justice".

Analysts say Pyongyang is receiving financial aid, military technology, and food and energy supplies from Russia in return for sending troops.

Kim also hailed efforts this year in "modernizing" the country's defences in the face of great "global geopolitical and technological changes".

Pyongyang's central committee began meeting on Tuesday, the same day North Korea fired a salvo of artillery from a multiple rocket launcher system, which analyst say could strike the South.

Last week, the South's dovish President Lee Jae Myung said he felt an apology was due to the North over his predecessor's alleged order to send drones and propaganda leaflets across the border.

Pyongyang has not responded to the overture from Lee, who has sought to mend fractured ties with the North.