The Philippines ordered the closure on Thursday of 21 mines, mainly nickel producers that account for about half of output in the world's top nickel ore supplier, in a government campaign to fight environmental degradation by the industry.

Manila also suspended operations at another six mines, including the country's top gold mine operated by Australia's Oceanagold Corp, as Environment and Natural Resources Secretary Regina Lopez vowed to put the public's welfare above mining revenues. 

"My issue here is not about mining, my issue here is social justice," Lopez, a staunch environmentalist, said at a briefing that showed footage of damage from mining to an audience including priests and residents of mining communities.

News of the mine closures sent global nickel prices higher and followed the earlier suspension of some operations amid an audit of the country's 41 mines that began shortly after outspoken President Rodrigo Duterte took office last June.