MANILA, Aug 18 — Two Chinese survey ships were spotted inside Philippine waters near the site of a confrontation between the countries in 2012 and threaten to further strain ties between the countries, President Benigno Aquino said.

“What are they doing there? What studies are they doing?” Aquino said on local news channel TV 5 in an interview that aired late yesterday. “I hope this does not lead to renewed tensions between our two nations.”

Tensions have been on the rise in the South China Sea as China becomes more aggressive in asserting its claims to about 90 per cent of the area, including over territory claimed by the Philippines, Malaysia, Brunei, Vietnam and Taiwan. The deepening spat with China prompted the Philippines to seek arbitration from the United Nations that the Chinese have rejected.

The Philippine military monitored the Chinese ships in the area of Reed Bank, 80 nautical miles from the western Palawan province and clearly within the Southeast Asian nation’s 200-nautical-mile exclusive economic zone, Aquino said.

“With all due respect, China seems to change like the seasons,” Aquino said. “There’s a season when they’re belligerent. There’s a season when they’re friendly. There’s a charm offensive one time, another time there’s none.”

Renewed Chinese presence in Reed Bank might lead to a “major escalation” of disputes if Chinese ships are “poised to harass” Philippine energy projects in the area, Richard Javad Heydarian, a political science lecturer at the Ateneo de Manila University, said by phone.

Chinese ships have been on “frequent sovereignty patrols” in Reed Bank and the Philippines is protesting this, Charles Jose, spokesman for the Philippine foreign ministry, said in an e-mail. “No other state is lawfully entitled to assert its sovereignty or sovereign rights over said area,” he said. — Bloomberg