Tens of thousands of people in an ethnic Mongolian region of northern China have joined rare protests and school boycotts against a new curriculum they fear will wipe out their minority culture, residents said Tuesday.

The policy change in Inner Mongolia means all ethnic minority schools in the remote region will now be required to teach core subjects in Mandarin rather than Mongolian, echoing similar moves in Tibet and Xinjiang to assimilate local minorities into the dominant Han Chinese population.

"Almost every Mongolian in Inner Mongolia is opposed to the revised curriculum," a 32-year-old herder from Xilingol League, who gave his surname as Hu, told AFP, warning Mongolian children were losing fluency in their mother tongue.

"In a few decades, a minority language will be on the verge of extinction."

Tensions flared across the vast grassland region bordering Mongolia and Russia after the policy was announced by the Inner Mongolia Education Bureau last Wednesday.

Mass demonstrations, with hundreds of parents and students facing off against police, have erupted across the region, according to video clips provided by residents to AFP, while thousands of students have boycotted classes.

"There are at least tens of thousands of people protesting across Inner Mongolia," Baatar, a 27-year old herder in Hinggan League who refused to give his real name out of security concerns, told AFP.

"Many parents are protesting outside schools, some with a few thousand parents outside, as well as ordinary people protesting on the street."

Enghebatu Togochog, director of the New York-based NGO Southern Mongolian Human Rights Organization, called the protests a "civil disobedience resistance movement" that has spread throughout Inner Mongolia, home to more than four million ethnic Mongolians who make up 16 percent of the region's population.

"Parents are refusing to send their children to schools that use Chinese as the only language of instruction," he said.

WeChat messages and photos of petitions against the policy written in the traditional vertical Mongolian script have been mass-censored by authorities in recent days, he added.

The Inner Mongolia Education Bureau did not respond to faxed requests for comment. It claimed in a Monday post that the number of Mongolian-language teaching hours remained unchanged.

It is the only region left in the world that uses the traditional Mongolian script, as neighbouring Mongolia adopted the Cyrillic alphabet under Soviet influence.

For decades, the region's bilingual curriculum for ethnic minority schools offered a full range of subjects taught in Mongolian, as well as Mandarin, English and Korean classes.

Herder Hu said that he and and many other Mongolians had become fluent in Mandarin while preserving their native language through this system.

Mongolians held a protest in the Mongolian capital on Monday against the move to Mandarin-only lessons in the neighbouring Chinese region.