An ethnic Mongolian herder has been killed in China in circumstances similar to an incident in May which led to protests in the region, reports say.

A human rights group said the herder had been trying to protect grazing land from Chinese oil trucks in Inner Mongolia when he was knocked down.

Chinese authorities said he had tried to overtake a truck on a motorcycle.

Thousands of ethnic Mongolians staged angry protests in May after a similar incident.

A herder named Mergen was killed on 10 May as he tried to stop a coal truck driving over pasture land.

His death led to a series of demonstrations in towns and cities across Inner Mongolia which the security forces acted quickly to put down. The truck driver who hit him was executed in August.

The latest incident occurred on Thursday in Uushin Banner district, near the city of Ordos, the US-based Southern Mongolian Human Rights Information Centre reports.

The herder, named Zorigt, was one of several who had been trying to protect their land "from unregulated Chinese oil and gas transport trucks that drive roughshod through their grazing lands and kill livestock", the group said.

The local government said in a statement on its website that he had been killed while trying to overtake the truck on a motorcycle.

The driver had been taken into custody, it added.

Ethnic Mongolians make up less than 20% of Inner Mongolia's population. They say Han Chinese settlers and developers are eroding their rights, especially with mining projects.

The region has traditionally been home to nomadic Mongolian herders, but has seen an influx of companies keen to exploit the region's resources.