North Korean leader Kim Jong-un promised to further develop his country's relationship with China and support their joint efforts to defend socialism, the North's official Korean Central News Agency (KCNA) reported Wednesday.

Kim's latest pledge came in a letter sent to Chinese President Xi Jinping, who earlier sent a congratulatory message on the 72nd anniversary of the foundation of North Korea.

"Kim Jong-un in his message expressed heartfelt thanks on behalf of the Workers' Party of Korea and the government and all the people of the DPRK and on his own behalf to the general secretary for extending warm congratulations and best wishes on the occasion of the 72nd founding anniversary of the DPRK," the KCNA reported.

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

Kim praised Xi and the Chinese communist party for successfully combating the novel coronavirus.

"Kim Jong Un expressed his will to do his best to develop, together with the general secretary, the DPRK-China friendship, valuable wealth and strategic choice of the two parties and the peoples of the two countries, into a fresh high stage in the joint struggle for defending and glorifying socialism," the report.

North Korea has yet to officially report an outbreak of the new coronavirus since shutting down its borders in early January. (Yonhap)