MANILA (Reuters) - The Philippines’ environment minister vowed not to buckle to mounting pressure on Thursday from a mining sector reeling from her shutting more than half of the country’s mines on environmental protection grounds.

Philippines' Environment and Natural Resources (DENR) Secretary Regina Lopez gestures during a news conference at the DENR headquarters in Quezon city, Metro Manila, Philippines October 14, 2016. REUTERS/Romeo Ranoco

Environment and Natural Resources Secretary Regina Lopez has ordered the closure of 23 of the country’s 41 mines, most of which produce nickel ore, and the suspension of five more due to violations uncovered during a lengthy environmental audit.

Mines ordered for closure include those run by Hinatuan Mining Corp, a unit of top Philippine nickel ore producer Nickel Asia Corp, and BenguetCorp Nickel Mines Inc.

The decision has rocked the global nickel market as the Philippines, an archipelago of more than 7,100 islands, is the world’s biggest exporter of nickel ore.

It also angered mining firms in the country who say the process followed by the minister was neither legal nor fair.

“I am not going to buckle,” she told Reuters after a closed-door meeting of an inter-agency mining council.

She co-chairs the council with Finance Secretary Carlos Dominguez. The panel sought a review of her decision to close the mines to ensure due process was followed and look into the impact on jobs and taxes.

“The (council) is recommendatory to me. They’re not my boss,” Lopez said. “Nobody can tell me what to do except the president.”

Damage to watersheds and siltation of coastal waters where the mines are located were the major reasons cited that led to Lopez’s decision to shut the mines.

“It’s totally in my right to close down the mines,” Lopez said in an earlier briefing and her decision has the backing of President Rodrigo Duterte, who has the final say on the fate of the affected mines.

Fifteen of the 23 mines ordered closed are within watershed areas.

Sources told Reuters that a team that reviewed an audit of the country’s mines recommended suspension of operations and payment of fines for environmental violations, rather than closures.

Lopez said it would take a miracle to convince her to allow mining in watersheds.

She said the mining companies can appeal her decision to the office of the president. If the president upholds the closure, they can go to court but they would have to halt operations while the matter is decided.

The Chamber of Mines of the Philippines is pressing the environment agency to release the audit behind the closures.