Chinese authorities have tightened security across the province of Inner Mongolia after days of unrest, rights groups and residents say. Hundreds of riot police armed with batons have been posted at the main square in provincial capital Hohhot. Access to the internet has been blocked in some areas, and universities and schools are under close watch. The unrest erupted last week after two ethnic Mongolians were killed in separate incidents. The demonstrations are thought to be the region's largest in 20 years, involving hundreds of ethnic Mongolians. The New York-based Southern Mongolian Human Rights Information Centre said more demonstrations had been planned for Monday. The centre described the situation in many parts of Inner Mongolia as martial law. Residents of the city of Chifeng told the Associated Press that police were out in force, and the internet had been cut off. "There's no point in going to the internet cafes since they have suspended business because the internet is down there too," said a waitress at a Chifeng restaurant. A university worker in Hohhot told Reuters that three entrances to the institution had been sealed off by police. Link: BBC News - China's Inner Mongolia 'under heavy security'