Witnesses said dozens of monks and other protesters were injured when security forces used incendiary devices that set fire to protesters’ encampments outside the offices of the Chinese company in charge of the project, which has a partnership with the powerful military in Myanmar, formerly Burma.
Photos from Burmese online news sites showed monks, who are highly revered in the country and are often involved in political causes, with singed saffron robes stuck to their badly seared skin.
The raid came hours before Daw Aung San Suu Kyi, the Nobel laureate and leader of the opposition in Parliament, was scheduled to visit the city of Monywa, near the mine.
Her visit underlined the widespread support the protests had engendered across the country before the raid.
Analysts said the brutal way that the crackdown was carried out could hamper Mr. Thein Sein’s efforts to persuade the country that his government has made a clean break from the military regimes that ruled the country for five decades.
“There will be political consequences,” said U Thiha Saw, the editor of Open News Journal and Myanma Danna magazine. “This may be the start of an uglier phase for the government. Things may get a little more complicated.”
The crackdown was conducted by security forces who have little experienced using modern crowd-control methods that are meant to minimize casualties. During military rule, dissent was brutally repressed and protesters on several occasions were shot dead in the streets.
In Thursday’s raid, security forces fired what one witness described to The Associated Press as “black balls that exploded into fire” to disperse the protesters, who had overstayed a Wednesday deadline set by the government to leave the area.
Factory workers and villagers, both ethnic Burmese and members of minorities, have taken advantage of new freedom under Mr. Thein Sein’s government to carry out limited demonstrations and strikes in recent months. The protests at the copper mine were by far the largest to appear since the former military junta ceded power to civilians in March 2011.
By dealing so forcefully with the mine protests, the government risks appearing to defend the vested interests of the old regime. The project is typical of the kinds of opaque deals often struck during military rule that have enriched many of the country’s generals. The military has been so deeply involved in business that it has its own holding company, the Union of Myanmar Economic Holdings; the company is listed as a part owner of the copper mine.
The deal between the military and the Chinese company, a subsidiary of a state-owned Chinese arms manufacturer, to expand the mine was signed two years ago when Mr. Thein Sein was prime minister under the military junta.
According to an American diplomatic cable made public by WikiLeaks, the deal was brokered by U Tay Za, a tycoon who became rich through his connections to the military regime, especially the country’s former dictator, Senior Gen. Than Shwe.
The crackdown may also complicate the investment picture for China, which has struggled in Myanmar with the perception that it is mainly interested in extracting natural resources from the country, not in aiding its development.
The Global Times, a state-owned Chinese newspaper, published an article Thursday, before the crackdown, that accused the West and advocacy groups of instigating the protests against the mine project, and said that shutting the mine down would be “a lose-lose situation” for the two countries.
“Chinese companies’ investments in Myanmar are facing huge challenges,” the article said. “What we see in the country is the inevitable impact of its democratization.”
Anti-Chinese sentiment was a major factor in the cancellation of a hydroelectric dam project last year in northern Myanmar that would have exported electricity to China. The project was suspended after an outcry.
Thursday’s raid came in the predawn hours. Ashin Visara, a 28-year-old monk who was injured in the crackdown, said security forces threw “explosive devices” into the areas where protesters were camped out.
“That started fires at the protest sites,” he said. “And then they attacked us.”
U Nway Oo, a student activist from Monywa who assisted the injured, said many protesters fled into the surrounding villages or the jungle.
“There were no medical personnel or ambulances around before the crackdown,” he said.
The mine, which is often referred to as Letpadaung for the mountains from which the copper is extracted, was initially operated by a joint venture between the Myanmar government and a Canadian company, Ivanhoe Mines. The Chinese company became involved two years ago. The expansion project would displace inhabitants of two dozen villages.
The protests have been led in part by two young women, Aye Net and Thwe Thwe Win, who reportedly escaped arrest.
The crackdown is a setback for the efforts of advocacy groups that focus on the crucial question of land rights, an issue likely to become more contentious as economic growth makes villagers’ land more attractive to companies and property developers. Land rights were the focus of a conference last weekend in the capital, Naypyidaw, that was attended by high-ranking government officials.
Wai Moe contributed reporting from Monywa, Myanmar.
