DHAKA: Philippine president Benigno Aquino said two Chinese survey vessels had been sighted in a gas-rich area of its exclusive economic zone, raising concerns of heightened tensions in the disputed South China Sea.

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 US$5 trillion of ship-borne goods pass every year.

‘Recently, we got a report from the armed forces that there were two hydrographic ships in Recto Bank, about 80 nautical miles off Palawan, clearly within our exclusive economic zone,’ Aquino told a television interview aired on Sunday, reports The Straits Times.

Recto Bank is also known as Reed Bank.

‘What are they doing there? What kind of studies are they conducting? I hope the presence of these ships will not lead to an increase tension between the two states.’

Tensions in the South China Sea between the Philippines and China began in 2011 when Chinese patrol boats harassed a survey ship hired by Anglo-Filipino Forum Energy PLC which won a contact to explore the Reed Bank.

BDST: 1230 HRS, AUG 18, 2014