Citizen activism has increased since the elected government took over last year. Street demonstrations have been legalized, and are generally tolerated, though detentions have occurred in sensitive cases.
Political and economic liberalization under Thein Sein has won praise from Western governments, which have eased sanctions imposed on the previous military government because of its poor record on human and civil rights.
The Letpadaung mine is a joint venture between China's Wanbao Mining Copper Ltd. and the military-owned Union of Myanmar Economic Holdings Ltd. Many in Myanmar remain suspicious of the military and see China as an aggressive and exploitive investor that helped support its rule.
In Yangon, more than 30 monks who staged a peaceful protest at downtown Sule pagoda, were joined by nearly 100 people who chanted prayers in front of the office of the army's holding company.
"May all be free from harm, may all be peaceful and may the Letpadaung mountains be green," they chanted in the Friday dusk.
Associated Press writer Matthew Pennington in Washington contributed to this report.
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