Beijing (CNN) -- Chinese authorities Monday arrested dozens of demonstrators in Hohhot as protests spread to the provincial capital and other cities in Inner Mongolia despite tightened security and reports of martial law, activists told CNN.

"Several hundred people, mostly students and ordinary Hohhot residents, gathered at Xinhua Square around 11 a.m. Monday, chanting slogans and holding signs demanding legal rights for the Mongolia people," said Enghebatu Togochog, director of the New York-based Southern Mongolian Human Rights Information Center. "Paramilitary troops dispersed the crowd after an hour and dozens were arrested."

Sources in the city told him the protest turnout was much smaller than planned, Togochog said, as officials sealed local campuses and shut down social media. He added that, in addition to Hohhot, the government has also deployed paramilitary troops into Tongliao, Chifeng and other cities, putting more areas in Inner Mongolia under de facto martial law.

Local officials continue to dispute activists' accounts, even as state-run media reported some conciliatory gestures by the government.

"There was no protest in downtown Hohhot," Wen Fei, an official with Inner Mongolia's foreign affairs office, told CNN. "Everything is normal and there is no martial law."

"All students are free to move around," echoed Ji Shugang, a spokesman for the government of Xilin Gol prefecture. "Journalists are welcome here, but you need to apply for permission first."

Xilin Gol is the site of one of the largest protests last week, as an estimated 2,000 Mongolian students took to the streets to show solidarity with a Mongolian herder, who was struck and killed by a Chinese coal truck driver.

In an unusual move, Inner Mongolia's Communist Party chief visited the Xilin Gol area Friday to meet with students and teachers, the Inner Mongolia Daily reported. Hu Chunhua said authorities had detained the suspects in the herder's death and promised swift punishment to those found responsible, according to the newspaper.

The government has also sacked a top local official and pledged to better manage the mining industry to reduce its impact on herders' livelihood.

The Beijing-based Global Times, a mass-circulating tabloid, ran an editorial Tuesday, calling some demands of "largely peaceful protesters" in Inner Mongolia "reasonable" while accusing Western media of exaggerating ethnic clashes in the region.

Activists acknowledge officials' effort to calm tensions, but doubted their sincerity in resolving the dispute long term. They say the government's push in recent years to expand coal mining in areas traditionally used for grazing has threatened the very existence of Mongolian herders and their culture.

"Officials just temporarily shut down a coal mine where the herder was killed," Togochog said. "Hu Chunhua still stated development must go on, so they won't halt coal mining and production in the area forever."

The grassroots and peaceful nature of the Mongolian demonstrations has made it difficult for authorities to justify a harsh crackdown, he added, noting Beijing's more heavy-handed responses in the past to protests by Tibetans and Uighur Muslims.

"By carrying out this non-violent movement, Mongolians are gaining confidence in people power, in its ability to demand changes," he said.

The Chinese government has hailed Inner Mongolia as a "model autonomous region" with rapid economic growth -- spurred by the mining industry -- and ethnic harmony. With the recent unrest gaining international attention, Beijing is playing down the ethnic dimension.

"Local authorities are trying to balance environmental protection and economic development," Foreign Ministry spokeswoman Jiang Yu commented Tuesday on the herder's death. "Overseas parties who try to use this incident to stir up trouble have ulterior motives."

Mongolians have lived in the area for centuries, but the Han Chinese -- who arrived in large numbers after the founding of the People's Republic in 1949 -- now make up almost 80 percent of Inner Mongolia's population.