BEIJING: China rejected Philippine complaints on Wednesday about Chinese survey vessels operating in a gas-rich area of Manila’s exclusive economic zone, and has lodged a separate complaint about the detention of Chinese workers, as tensions persist.

Philippine President Benigno Aquino said over the weekend that two Chinese survey vessels had been sighted in part of the disputed South China Sea also claimed by the Philippines called Reed Bank.

In a statement faxed to Reuters, China’s Foreign Ministry said that Reed Bank was Chinese territory.

“Survey activities being carried out by Chinese survey ships are appropriate, legal and beyond reproach,” the ministry said.

China claims almost the entire South China Sea, believed to be rich in deposits of oil and gas resources. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also claim the sea where $5 trillion of ship-borne goods pass every year.

Tensions in the South China Sea between the Philippines and China began in 2011.