Chinese President Xi Jinping, left, and North Korean leader Kim Jong-un wave from an open top limousine as they travel along a street in Pyongyang during Xi's visit in this June 20, 2019, photo. AP-Yonhap

Leaders of China and North Korea on Sunday traded a vow of enhanced bilateral cooperation on the 75th anniversary of the establishment of diplomatic relations between the two countries, state news agency KCNA reported.

"I attach great importance to the development of the China-DPRK relations and have jointly led and promoted the in-depth development of the China-DPRK relations while maintaining close communications with you, Comrade General Secretary, through several meetings and personal letters and messages in recent years," China's President Xi Jinping said in his message to North Korean leader Kim Jong-un on Sunday.

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

He said China was ready to continue to "write a new chapter" of relations through strengthened communications and cooperation.

China is by far North Korea's largest trading partner, and the two share a history going back to Beijing's support of Pyongyang during the 1950-1953 Korean War.

But China this year reacted guardedly as Kim deepened ties with Russian President Vladimir Putin. This year, North Korea and Russia signed a strategic treaty that includes mutual defense elements.

Kim also pledged to "steadily strive to consolidate and develop the friendly and cooperative relations between the DPRK and China as required by the new era," in his message to Xi Zinping on Sunday.

In the meantime, Kim oversaw a live artillery firing by graduates of O Jin-u Artillery Academy on the eve of their becoming commanding officers of the core arm of the country's armed forces, the KCNA reported on Sunday. The facility trains the backbone of the country's artillery force.

On Friday, Kim said the country would not hesitate to use all available offensive forces including nuclear weapons if the enemy attempted to use force to encroach on its sovereignty. (Reuters)

Kim Jong-un talks to officers during his visit to O Jin-u Artillery Academy, Oct. 5, in this photo provided by North Korea's Central News Agency. Yonhap