Chinese troops have cleared tens of thousands of mines from one million sq.m. of land along the Sino-Vietnamese border in an operation that began last November, Xinhua news agency reported on Tuesday.

Qiu Daxiong, deputy commander of the Guangxi Military Area Command, said the operation, the second since the early 1990s when China and Vietnam restored diplomatic relations following their border conflict in the 1980's, is expected to clear 120 zones on nearly 20 million sq.m. of ground within three years.

"Some tens of thousands of mines consisting of 18 types were removed or exploded in one month," the agency said.

Qiu said that many of the mined areas are on mountainous slopes where people did not want to risk their lives.

The grass there is head high and "even the most advanced mine detectors are of little use", so Chinese troops have to use explosives to remove mines buried beneath the surface, the agency said.

In the minesweeping action in 1993, border defence troops in Guangxi removed more than 600,000 mines and restored 18,000 hectares of farmland.

The operation also helped open 25 border trade sites and nine ports of entry for border trade between the two countries.