YANGON, Burma (AP) — Students have joined farmers and other protesters against a land grab for a copper mining project in northwestern Burma.

The student activists from the city of Mandalay joined Tuesday’s protest in Monywa in northwestern Sagaing region after police arrested 12 demonstrators on Monday. Land rights activist Win Cho in Yangon said Wednesday that nine were released but three female protest leaders remain in custody.

An activist in Monywa who spoke anonymously said as many as 1,500 protesters marched Tuesday. Most were farmers and local residents.

They began protesting in August that they consider the seizure of nearly 8,000 acres (3,250 hectares) of land unfair. The Monywa mine project is a joint venture of a military-controlled holding company and a Chinese company.