China is to build its first military base in Afghanistan for hundreds of troops carrying out counter-terrorism training missions across the border from its western Xinjiang region, according to reports.

The base will be only the second overseas site for the increasingly active Chinese military, coming a year after a base was opened in Djibouti on the Horn of Africa.

Around 500 troops will be stationed in the base training their Afghan counterparts in the remote Wakhan Corridor in the north east province of Badakhshan, the South China Morning Post reported.

The report, which was denied by the Chinese government, said work had already begun at the site.

China has long worried that instability in Afghanistan could spill over into Xinjiang or that it could damage its economic plans for a 21st century Silk Road in the wider region.

Beijing has been accused of conducting a severe security crackdown on the Xinjiang's Muslim Uighur minority, but says it is tackling Islamist violence. Hundreds have died in the violence.