PAJU, South Korea, March 17 -- China and South Korea on Monday started encoffining remains of Chinese soldiers killed in the Korean War in South Korea's border city of Paju.

A total of 437 remains of Chinese soldiers along with some of their clothes, helmets, bottles and other belongings were covered with traditional Korean papers and placed in coffins supplied by Chinese government. 55 of the remains were attached with identification records.

Both Chinese and South Korean officials mourned for the soldiers and presented flowers to their remains.

"We want to express our deep gratitude to South Korean government and all the people who have contributed to the return of the remains of Chinese soldiers," said Li Guiguang, an official from China's ministry of civil affair.

He added that it was a significant event for leading China-ROK relations to a new stage and both sides would continue to fulfill all the following tasks.

The excavation in Paju started in December 2013 and lasted for three months as solders' remains have to be cleaned, dried and identified in extreme cold winter.

Around 14,000 South Korean soldiers, experts and technicians were involved in the excavation and identification procedures, according to Seoul's defense ministry.

"The return of Chinese soldiers' remains was a milestone of healing the wounds of war both countries suffered," said Moon Sang Gyun, an official from South Korean defense ministry.

He said South Korea has made great efforts on the issue as it was their promises to the Chinese side.

Seoul and Beijing reached an agreement last year with Seoul promising to return the remains of Chinese soldiers buried in a cemetery in Paju. This move came after South Korean President Park Geun-hye's visit to China in June last year.

The coffins will be carried back to China by air after a transfer ceremony at South Korea's Incheon Airport in late March, several days before the traditional Chinese Tomb-Sweeping Day, according to South Korean defense ministry.

The Chinese People's Volunteers (CPV) fought side by side with the people's army of the Democratic People's Republic of Korea in the 1950-1953 Korean War against South Korean army and U.S.-led UN forces. Tens of thousands of CPV soldiers died on the Korean Peninsula during the war that ended in armistice.

Since 1981, a total of 43 remains of Chinese soldiers have been returned by South Korea via the United Nations Military Armistice Commission.