Output of nickel ore for direct shipping fell to 9.34 million tonnes in July-September from 11.09 million tonnes in the same period last year, data from the Mines and Geosciences Bureau showed.
The Philippines` output of nickel ore fell 16 percent in the third quarter from a year earlier.
The Philippines is the biggest supplier of nickel ore to China, where the metal is used to make stainless steel. Eight of the 10 suspended mines are nickel producers, and along with 14 of the 20 facing suspension, they accounted for more than half of the Philippines` nickel ore output last year.
Production dropped to 19.8 million tonnes in the nine months to September from 25.97 million tonnes a year ago, according to the data.