Below is a video published by NHK

Chinese authorities are intensifying their crackdown in the Inner Mongolia Autonomous Region on ethnic Mongolians who are staging protests against measures to reduce education in their native language.

The central government has decided that language classes for the first and seventh grades should teach Chinese, rather than Mongolian, from the new school term that began this month.

It has also been decided that classes in other subjects will be switched to Chinese in phases from next year.

Mongolians are concerned that their language could be lost. Local residents say demonstrators and parents of children who boycotted classes have been detained.

A former teacher told NHK by phone that many people have been arrested for allegedly staging illegal rallies and treated like political prisoners.

She said teachers who oppose the new policy are threatened with dismissal or pay cuts.

A US-based organization, Southern Mongolia Human Rights Information Center, estimates that more than 4,000 Mongolians have been "under some form of police custody" since late August.

Back on September 3, a Chinese Foreign Ministry spokesperson said a country's official language is a symbol of national sovereignty, and that learning and using it is people's right and obligation.

The spokesperson stressed that education in Inner Mongolia will continue to be taught in the two languages.