China has touted its intervention in the 1950-53 Korean War as an "indelible mark on history" of its friendship with North Korea after the North's leader Kim Jong-un paid tribute to the Chinese soldiers killed during the war.

The Korean War broke out on June 25, 1950, when tank-led North Korean troops invaded South Korea. The United States and 20 other allied countries fought on the side of South Korea under the United Nations flag, while Chinese soldiers came to help North Korea. The conflict ended in a cease-fire on July 27, 1953.

The North's young leader Kim laid a wreath at a cemetery of Chinese war dead earlier this week in the wake of the 62nd anniversary of the end of the war.

Asked about Kim's tribute to the Chinese war dead, China's foreign ministry spokesman Lu Kang said in a brief statement, "The historic contribution made by the Chinese People's Volunteer Army to maintaining peace and China-DPRK (North Korea) friendship will leave an indelible mark on history."

It was China's first official response to Kim's tribute, and the statement was posted on the Chinese ministry's website late Tuesday.

China's state-controlled media organizations have showed keen attention to the tribute.

Political ties between North Korea and China, once billed as close as "lips and teeth," remain strained over the North's defiant pursuit of nuclear weapons.

Diplomatic sources said China has invited Kim to attend events in Beijing marking the 70th anniversary of the end of World War II, but it is unclear whether he will accept the invitation.

Despite warming ties between South Korea and China, the Chinese view of how the Korean War started remains controversial.

China's school textbooks stop short of mentioning that North Korea's invasion sparked the Korean War, and the Chinese Communist Party officially refers to the three-year conflict as "The War to Resist the U.S. and Aid North Korea." (Yonhap)