Russian President Vladimir Putin greets North Korean leader Kim Jong-un as Kim visits Vostochny Cosmodrome in Russia, Sept. 13, 2023. Yonhap

North Korean leader Kim Jong-un has sent a congratulatory message to Russian President Vladimir Putin for formally starting his fifth term as Moscow's leader, state media said Wednesday, amid deepening military cooperation between the two nations.

Putin began his fifth term Tuesday, extending his 24-year rule for another six years after winning a landslide victory in Russia's election in March.

"The respected Comrade Kim Jong-un warmly congratulated Putin once again on his inauguration as the president of the Russian Federation and wished him great successes in his responsible work for Russia and its people," Kim was quoted as saying in a dispatch released by the Korean Central News Agency.

The letter was delivered through the Russian Embassy in Pyongyang, it added.

It marked the second congratulatory message Kim sent to Putin on his reelection. In March, Kim sent a letter vowing to "bring about a new era of the DPRK-Russia friendship ... in conformity with the requirements of the times and push forward with the accomplishment of the cause of building a powerful country."

DPRK stands for the North's official name, the Democratic People's Republic of Korea.

The latest message came as North Korea-Russia ties have been significantly deepening following a rare summit between their leaders in September, spawning speculation over Pyongyang's arms transfers to Moscow for use in its war in Ukraine.

Last week, the White House said Russia delivered more than 165,000 barrels of refined petroleum to North Korea in March alone, noting that such shipments have exceeded the annual cap of 500,000 barrels set by the U.N. Security Council sanctions imposed on North Korea in 2017. (Yonhap