KUNMING, Nov. 21-- A landmine-sweeping mission has begun along the Sino-Vietnam border in south China's Guangxi Zhuang Autonomous Region, clearing the dangerous historical legacy to enable border development.

Twenty-one explosions were heard in Pingxiang City on Friday as dozens of People's Liberation Army (PLA) soldiers detonated mines in the nearby minefield.

It is part of the country's third large-scale de-mining missions since the 1990s, which began in southwest Yunnan Province on Nov. 3.

Hundreds of thousands of landmines were laid along the border during confrontations between the two countries from 1979 to 1989.

De-mining will help the opening up and development of the border region, said Yan Lixiang, deputy chief of staff of the PLA Guangxi Regional Military Area Command.

The Guangxi mission covers 53 minefields in eight cities and counties and is scheduled to complete before 2017.

China 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.