Protests which have rocked parts of China's remote and vast northern region of Inner Mongolia appeared to subside on Saturday, though residents reported a heavy police presence and one said "martial law" was still in place.
China has sealed off some counties in Inner Mongolia, a resource-rich region strategically located on the borders of Russia and Mongolia, after recent demonstrations sparked by the hit-and-run death of a Mongolian herder.
Residents have told Reuters parts of Inner Mongolia have been placed under martial law.
The New-York-based Southern Mongolian Human Rights Information Centre said in an emailed statement that the government had ordered a sweeping crackdown, shutting off universities and arresting at least 40 people.
In regional capital Hohhot, it said all schools and universities were under police guard.
"School authorities are ordered to count their students in their dorms regularly to make sure no students (are) missing," the group said.
The protests were set off by the death earlier this month of a Mongolian herder, Mergen, who was killed when he was struck by a coal truck. The government announced the arrest of two Han Chinese for homicide, but that failed to stem public anger.
Residents reached by telephone on Saturday in Shuluun Huh Banner, or Zheng Lan Qi in Chinese, and Left Ujumchin Banner, or Xi Wu Qi in Chinese, two places which have witnessed protests, said the situation remained tense.
"I've not seen any protesters today but there is still martial law. All bus services have been stopped," said one resident in Left Ujumchin Banner who declined to be identified.
Another resident said no vehicles from outside had been allowed entry.
In Shuluun Huh Banner, a resident said: "They were protesting yesterday in front of the government. I don't think they are there today. There are still lots of police around."
An official reached by telephone at the Left Ujumchin Banner government denied there had been any unrest.
"I've not heard of this. Everything is normal," said the official, who then hung up the telephone. Repeated telephone calls to the Shuluun Huh Banner, or county, government, went unanswered.
The Southern Mongolian Human Rights Information Centre said Shuluun Huh Banner's main town was "under complete control of riot police and army. Reportedly more reinforcements are on their way".
"REAL GROUNDS FOR CONCERN"
Amnesty International said it was concerned the protests could attract a heavy-handed response. "Given the heavy handed repression of similar protests in other regions, like Xinjiang and Tibet, there are real grounds for concern about the situation in Inner Mongolia," Catherine Baber, Amnesty's Asia Pacific deputy director, said in an emailed statement.
China's Mongolians, who make up less than 20 percent of the roughly 24 million population of the Inner Mongolian Autonomous Region, rarely take to the streets, unlike Tibetans or Xinjiang's Uighurs, making the latest protests highly unusual.
National-level state media has not reported on the unrest and the government, wary of any signs of instability, has moved to block discussion of the incidents on the internet, though some pictures and comments have gone through.
"Mongolians have lived there for thousands of years. But more and more Han Chinese are moving to Inner Mongolia. The guest is now the master. The grasslands are destroyed and the deserts spreading," wrote "Xinjiang Stars" on popular microblogging site Weibo.
The demonstrations have broadened their scope, with those taking part demanding greater official protection for their culture and traditional way of life.
Inner Mongolia, which covers more than a tenth of China's land mass and borders Mongolia proper, is supposed to offer a high degree of self-rule.
In practice, though, Mongolians say the Han Chinese majority run the show and have been the main beneficiaries of economic development.
Inner Mongolia is China's largest producer of coal, a commodity that feeds well over half the country's power plants and on which China depends for its breakneck economic growth.