Beijing - Ethnic Mongolian activists have issued online calls for protest following the death of a Mongolian man who had tried to block a truck from crossing grassland in China's Inner Mongolia region, a US-based rights group said on Tuesday.

The activists issued a notice in Mongolian and Chinese for 'demonstrations calling for the protection of herders' rights', according to a translation by the Southern Mongolian Human Rights Information Centre.

The notice said a 'courageous herder', identified by the single name Zorigt, died on Thursday while 'defending his grazing land and his inalienable right as the owner of the land' in Uushin Banner in Inner Mongolia's Ordos district.

'This notice is issued to call for a region-wide demonstration in all (areas) where Mongolians reside,' it said.

It said the protests were designed 'to obtain a satisfactory response from the Inner Mongolian authorities to fulfil their promises to protect herders' rights and regulate the mining industries'.

There were no immediate reports of any protests on Tuesday.

The rights centre said authorities in Uushin Banner were 'tightening surveillance', had banned all forms of gatherings by Mongolians, and had warned Zorigt's relatives not to discuss his death.

The protest calls follow the death of two Mongolians in clashes with truck drivers and coal miners in May.

The two deaths set off the largest protests by Mongolians in Inner Mongolia for 20 years, with thousands of people gathering in several town and cities in late May and early June.

Following the protests, Chinese leaders promised to improve the economy and environment of the vast Inner Mongolia region.

But state media quoted officials as saying Inner Mongolia would remain at the forefront of a national plan to expand coal production by developing large open-cast mines.

The government said local courts would try a total of four people on charges of murder linked to the two earlier deaths.

A coal-truck driver was executed in late August for causing the death of one of the Mongolians.

About 4 million ethnic Mongolians live in China, most of them in Inner Mongolia, where they now make up less than 20 per cent of the region's population of more than 20 million.

Many Mongolians resent what they perceive as encroachment by the majority Han Chinese population upon the region's grazing lands.