North Korean leader Kim Jong-un, right, walks with Chinese President Xi Jinping during his visit to Beijing on March 28, 2018. Yonhap

North Korean leader Kim Jong-un sent his congratulations to Chinese President Xi Jinping after Xi was appointed as leader of the country for an unprecedented third term, its state media reported Sunday.

Kim sent the letter after the Central Committee of the Communist Party of China (CPC) formally reelected Xi the party's general secretary for another five years, according to the official Korean Central News Agency (KCNA).

"Please accept my warmest congratulations to you upon the glad news that the 20th Congress of the CPC was successfully held and you were elected again as the general secretary of the Party Central Committee," read the message carried by the KCNA.

Kim said Xi's re-election offered "a significant landmark" for China and its people, and expressed hope for the two nations to strengthen their ties.

"I, together with you, will shape a more beautiful future of the DPRK-China relations meeting the demand of the times and lead the endeavors for its realization so as to continue to powerfully propel the socialist cause in the two countries," Kim said, referring to North Korea's official name, the Democratic People's Republic of Korea.

China is North Korea's key ally and economic benefactor, with their relationship forged in blood during the 1950-53 Korean War. (Yonhap)