North Korean leader Kim Jong-un visits the Friendship Tower in Pyongyang, on Friday, a day ahead of the signing of the armistice that ended the 1950-53 Korean War. (Yonhap)

North Korean leader Kim Jong-un has said "kindred" relations with China will be "firmly" carried forward as he visited a monument symbolizing bilateral ties, state media reported Saturday, amid suspected signs of strain between the traditionally friendly countries.

On Friday, Kim visited the Friendship Tower in Pyongyang, which was erected to commemorate China's participation in the 1950-53 Korean War, and paid tribute to fallen Chinese soldiers during the war, a day ahead of the 71st anniversary of the armistice that ended the conflict, according to the Korean Central News Agency (KCNA).

"He expressed belief that the DPRK-China friendship established as the ties of kindred would be firmly carried forward and developed along with the immortal spirit of the martyrs," the KCNA said in an English-language dispatch.

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

The Korean War, which started with an invasion by North Korea, ended in a truce, not a peace treaty, on July 27, 1953. North Korea celebrates the armistice signing date as Victory Day, claiming it won what it calls a liberation war against US-led aggression.

Kim's visit came as the North has appeared to be aligning closer to Russia and away from China, with North Korean leader Kim Jong-un and Russian President Vladimir Putin signing a "comprehensive strategic partnership" agreement during their summit in Pyongyang last month.

Earlier this month, the Rodong Sinmun, the newspaper of the North's ruling party, did not carry any articles on the anniversary of the signing of the friendship treaty between North Korea and China as it had done so on the anniversary date in the past. (Yonhap)