KUNMING, Nov. 16 (Xinhua) -- The third landmine-sweeping mission in the Yunnan section of the Sino-Vietnamese border in southwest China was completed Friday, ending a dangerous historical legacy that had hindered border development, according to local authorities.

Hand-in-hand, soldiers ceremonially walked across part of the minefield in the border county of Malipo before handing the landmine-free field over to the locals, according to People's Liberation Army (PLA) Yunnan Provincial Military Area Command.

About 200,000 explosives in over 50 sq km of minefield covering more than 30 townships in six counties in Yunnan have been found and detonated since the latest round of de-mining in the province started in 2015.

More than 400 PLA officers and soldiers, according to different terrain conditions, took measures including manual sweeping, exploding mines, setting fire to destroy mines, as well as mechanical and robotic sweeping.

Chen Anyou, head of the Yunnan de-mining troop, said the mission this time was more complicated and dangerous, as the minefield was in a "tough region" left by previous missions.

"Thousands of mines could be found in every square kilometer and some parts of the minefield were even on mountains at slopes of more than 60 degrees," he said.

"In the past, landmines often caused injuries to locals, making it very dangerous to farm the land," said local resident Pan Jinliang. The 57-year old lost his legs in 1992 and 2016 due to an accidental mine explosion when farming.

"I really want to thank the de-mining soldiers, our heroes, who made our lives return to normal and our children no need to be afraid of explosions," he said.

The troop is also expected to help local government permanently seal the minefield of over 20 sq km by the end of the year.

The landmine-sweeping mission in Yunnan is part of China's third large-scale de-mining missions since the 1990s. The country conducted two large-scale de-mining campaigns from 1992 to 1994 and from 1997 to 1999. From 2001 to 2008, Chinese soldiers also cleared mines for a boundary demarcation project.

Last month, south China's Guangxi Zhuang Autonomous Region announced its completion of the third landmine-sweeping mission in the Guangxi section of the Sino-Vietnamese border.