China expressed concern on Thursday after the Philippines' energy department said it would not renew visas for 16 Chinese nationals who work for the Philippine national grid after a senator raised security concerns.
The state-owned State Grid Corporation of China has a 40 percent stake in the National Grid Corporation of the Philippines.
This week, the Philippines energy minister said that come July, only two Chinese nationals would remain with the company, who would only be there in their capacity as board directors.
Chinese Foreign Ministry spokesman Hong Lei said the Chinese firm had made important contributions to building the grid in the Philippines.
"(We) hope that the Philippines side can fairly and justly handle the relevant issue, earnestly uphold the legal rights of the Chinese company operating in the Philippines and create a good investment environment for foreign investors," he told reporters.
China and the Philippines are engaged in an increasingly ugly dispute over ownership of islands in the South China Sea.
China claims 90 percent of the South China Sea, believed to have huge oil-and-gas deposits and rich in fishery resources, based on a much-disputed map drawn in mid-20th century. Brunei, Malaysia, the Philippines, Vietnam and Taiwan also have claims over the sea where about $5 trillion of ship-borne trade passes every year.