The Philippines' environment minister on Tuesday ordered the cancellation of 75 mining contracts, stepping up a campaign to stop extraction of resources in sensitive areas after earlier shutting more than half of the country's operating mines.

The contracts are all in watershed zones, with many in the exploration stage. They cover projects not yet in production and the latest action by Environment and Natural Resources Secretary Regina Lopez suggests she will not allow them to be developed further.

"You kill watershed, you kill life," Lopez told a news conference.

A longtime environmentalist, Lopez ordered the closure of 23 of the Philippines' 41 mines on Feb 2 for damaging watersheds and for siltation of coastal waters and farmlands. Another five mines were suspended, causing an outcry from the industry.

The contracts ordered canceled on Tuesday, known as mineral production sharing agreements, include the $5.9 billion Tampakan copper-gold project in South Cotabato province in Mindanao Island, the biggest stalled mining venture in the Southeast Asian country.

Tampakan failed to take off after the province where it is located banned open-pit mining in 2010, prompting commodities giant Glencore to quit the project in 2015.

"We're canceling this as a gift of love to the people of Cotabato," Lopez said.

A few miners facing a shutdown of their operations have threatened legal action, with some saying on Tuesday they have received a formal closure order from the environment agency.

Top Philippine nickel ore producer Nickel Asia Corp said it "will pursue all legal remedies to overturn the said order because of due process violations and the absence of any basis" that would warrant a suspension or closure of operations of its unit Hinatuan Mining Corp.

Hinatuan was told that its operation has "impaired the functions of the watershed in the area", according to a copy of the closure order.